Giraffe Overseer - Akk Lab/Animal 5, an artist off of pinterest.com really nice work.
Void Walk - Art is from w-dog.net, artist is unknown as far as I researched, tried to give credit but still giving credit to the site.
Gireaffe of the Clouds - Google Images
Mother Giraffe - Google Images
Wall of Divine Intervention - Google Images
In the future, please post text versions of your cards.
As for your cards:
Giraffe of the Clouds is very undercosted and is probably too breakable. It doesn't do much on its own other than protect up to two of your dudes from spot removal while possibly stopping an attacker, but with literally any card that has a beneficial "enters the battlefield" trigger for your other creatures, this card is crazy powerful. This is the kind of thing that would normally be costed at 7 cmc or above because of how good of a combo piece it can be. Just look at Wispweaver Angel. That card is very similar, but can only flicker one thing and doesn't have flash. Sure, it's a 4/4 flier, but I'm fairly sure they gave it those stats so that they could cost it higher. This is just not the kind of card that should be cheap to cast.
Giraffe Overseer seems fine, if a little underpowered. I think its power level seems good for uncommon.
Mother Giraffe (is Giraffe tribal a thing in your set?) seems like another uncommon-tier card. Or a throwaway junk rare. Not exciting or particularly good, but it gives you slightly more value than what you pay for.
Void Walk actually seems overcosted to me. I could see this at 4 or even 3 cmc in 2 colors at rare, especially considering it puts your stuff back tapped. Also, I don't see the need to have double white and double blue.
The last one is tricky, and is the only one here that really seems mythic to me. The wording doesn't work, but I see what you're trying to do. Hexproof prevents you from changing the target of an opponents spell to this guy, so you'd have to reword it. I might try something like:
"If a spell or ability an opponent controls would destroy or exile another creature or planeswalker you control, you may exile ~ instead.
All noncombat damage that would be dealt to you or another permanent you control is dealt to ~ instead."
There are small interactions that would be different, but overall, I think this works in the rules and does what you need. I would also increase the mana cost on this one too. Empyrial Archangel is very similar and costs 8. Even considering the higher power, that still tells me that this card should cost around the same. Probably around 6.
All around, pretty neat designs. Nothing really new or exciting, but mostly good.
Giraffe of the clouds goes infinite with 2 of itself and any etb creature.
Overseer is pretty much a blue Wall of Omens, seems fine.
I don't understand why mother giraffe has reach, 6 power over 2 bodies for 4 mana is already very good (Especially with the flicker theme)
Void Walk looks correctly costed, there's some very interesting interactions you can do with it. Such as protecting your team from removal/wraiths, cast it during your end step to have no board from your opponents turn, so they can't interact with you, preventing combat damage dealt to your blockers.
Wall of Divine Intervention doesn't work at all, first you can't redirect your opponents spells to your creatures with hexproof, next magic cards can't see the future, there's no way to tell if a spell or ability will destroy, damage or exile a permanent until it happens, that's what replacement effects are for.
I want to also point out that void walk kills all your auras, or at least forces you to put them on things you don't control, because you probably won't be controlling anything when they return.
Also that it returns things you controlled but didn't own under their owner's control, not yours, but you may or may not have intended that one.
Void Walk - Art is from w-dog.net, artist is unknown as far as I researched, tried to give credit but still giving credit to the site.
Gireaffe of the Clouds - Google Images
Mother Giraffe - Google Images
Wall of Divine Intervention - Google Images
As for your cards:
Giraffe of the Clouds is very undercosted and is probably too breakable. It doesn't do much on its own other than protect up to two of your dudes from spot removal while possibly stopping an attacker, but with literally any card that has a beneficial "enters the battlefield" trigger for your other creatures, this card is crazy powerful. This is the kind of thing that would normally be costed at 7 cmc or above because of how good of a combo piece it can be. Just look at Wispweaver Angel. That card is very similar, but can only flicker one thing and doesn't have flash. Sure, it's a 4/4 flier, but I'm fairly sure they gave it those stats so that they could cost it higher. This is just not the kind of card that should be cheap to cast.
Giraffe Overseer seems fine, if a little underpowered. I think its power level seems good for uncommon.
Mother Giraffe (is Giraffe tribal a thing in your set?) seems like another uncommon-tier card. Or a throwaway junk rare. Not exciting or particularly good, but it gives you slightly more value than what you pay for.
Void Walk actually seems overcosted to me. I could see this at 4 or even 3 cmc in 2 colors at rare, especially considering it puts your stuff back tapped. Also, I don't see the need to have double white and double blue.
The last one is tricky, and is the only one here that really seems mythic to me. The wording doesn't work, but I see what you're trying to do. Hexproof prevents you from changing the target of an opponents spell to this guy, so you'd have to reword it. I might try something like:
"If a spell or ability an opponent controls would destroy or exile another creature or planeswalker you control, you may exile ~ instead.
All noncombat damage that would be dealt to you or another permanent you control is dealt to ~ instead."
There are small interactions that would be different, but overall, I think this works in the rules and does what you need. I would also increase the mana cost on this one too. Empyrial Archangel is very similar and costs 8. Even considering the higher power, that still tells me that this card should cost around the same. Probably around 6.
All around, pretty neat designs. Nothing really new or exciting, but mostly good.
Overseer is pretty much a blue Wall of Omens, seems fine.
I don't understand why mother giraffe has reach, 6 power over 2 bodies for 4 mana is already very good (Especially with the flicker theme)
Void Walk looks correctly costed, there's some very interesting interactions you can do with it. Such as protecting your team from removal/wraiths, cast it during your end step to have no board from your opponents turn, so they can't interact with you, preventing combat damage dealt to your blockers.
Wall of Divine Intervention doesn't work at all, first you can't redirect your opponents spells to your creatures with hexproof, next magic cards can't see the future, there's no way to tell if a spell or ability will destroy, damage or exile a permanent until it happens, that's what replacement effects are for.
Also that it returns things you controlled but didn't own under their owner's control, not yours, but you may or may not have intended that one.