Well I really have participated a lot in games in my church and together with the youth.
Well I have a few game ideas:
1) This is called the mimic game..
Where you tell the groups to split up and have each group choose a passage from the New or Old Testament, and then have them incorporate that passage. Who ever interprets the better will win the game. You could do this a few times if the groups really get excited.. But it takes a while for them to prepare a piece to show, so normally this is done only once. We, each group took 20 minutes to prepare each piece to then present it and see which one is better, of course it has to be judged by others.
2) The song game..
You have some song tittles written on a index card. Then you have your groups away from you, you start to sing the songs and the person , representing the group, that comes towards you first to continue to sing the same song wins the points.. You could do this a few times if you see that they are interacting well with knowing the songs and are really competing.
3) Old fashioned Bible Games..
These are just regular games where you prepare dozens of questions from the bible, and have the references written down from where you took your question. Then just have people take turns on answering and finding the bible references to answer the question. Remember that groups work better than crowds. So have them always in groups, because sometime on a huge crowed everyone will participate at least most of them, and in individual crowded games were everyone if for them solve, normally fewer people participate and even fewer stand out, or are willing to answer and interact.
Well those are just some tips, I know you could find lots more online, if you have any questions let me know..