help with iphone 3GS performance (polys and audio)

There are quite a few articles out there that cover optimization in a lot of detail, but in general, you want to stay under 7.5k triangles in your scene, stay under 20 draw calls & atlas your textures. You could batch draw calls too, and you can also use object occlusion culling, so it will disable objects that aren't in view, occluded by other objects.

couple of places to start for optimizing are here and here but your best bet is googling iphone optimization unity.

Not sure I understand the question about the texture, but here are instructions on how to add a gui texture as a background.

tnkx taters, the thing that i'm really looking for is the size of the type of files that iphone 3GS can handle for a best performance, but your info has been really helpful!