silvercut; Pichoro has made a much more advanced version of the booster pack generator; I don't know whether it includes the functionality you want, but it can be found here: http://mtg.pifro.com/viewtopic.php?t=453
zeppelined; Prowl uses the cards own subtypes, just like on real magic cards. So, for instance, if you wanted to make a prowling sorcery, you'd need to give it creature subtypes by making it a Tribal also.
Oooooh, thank you very much! The Tribal mechanic always confused the heck out of me. I got it now.
I've looked around but can't find the answer to this: how do you set the subtype parameter if you're using Prowl? It doesn't give any place to type it in (like it does for cost, for instance). I tried typing in the subtype I wanted in various places in the card text box to no avail. (by the way, MSE is awesome)
Oooooh, thank you very much! The Tribal mechanic always confused the heck out of me. I got it now.