I have been looking for some. The only one I have found is Adolifs...
... and it looks more like trash then a Flood...

thanks :P that will go great with one part of my map. Now I just need 1 or 2 ground customs...

have you tried making your own?

Keep in mind, people want to properly allocate and use their time for different things. Not everyone wants to/can make their own stuff when you have perfectly functional stuff done already. Modelling the biped (task enough), then rigging (task enough enough), then having it work in-game (not as tough as the last two if the last two are done right to begin with) take a lot of time to accomplish and people simply want to do other things during that time. It's not that I'm saying "USE RIPS" or anything of that sort, but I have found time is more valuable of a resource than having 100% custom content. To balance this out, that's what crediting the original source of the work is for.

@OP: Regardless, I would suggest using stock Flood bipeds for placeholders to where whatever AI scenario your planning is done schematically, then create your own content if necessary.

You forgot animating too, and unwrapping your model to fit a texture.

I've always said this, that all it takes is a bit of dedication to get what you need. In the long run, creating your own custom content is better for everyone, as it avoids the drama which can happen, over someone ripping content that the author claims isn't theirs, and not to mention, when you finish something you know you've made from scratch, you not only feel a sense of pride for doing it, but you've also learned something.

Yes, creating custom is hard, but I was just suggesting if you couldn't find any, then the best way would probably try to make it.