The only conditions are....
No Heretics, so no Chaos basically.
No well known chapters, so don't be asking for something like Crimson Fists for example.
Pictorial List A-L http://wh40k.lexicanum.com/wiki/Pictorial_List_of_Space_Marine_Chapters_A-L
Pictorial List M-Z http://wh40k.lexicanum.com/wiki/Pictorial_List_of_Space_Marine_Chapters_M-Z
Just pick one and post a comment saying which one you want to see.
Also, I'm not sure at what amount I will do it but at a certain amount of Marines I'll be making a diorama involving them.
So that's something to look forward to.ise of what the first chapter will be