Texture resolution question

Hello everyone,
I am modeling props for iPhone 4/ iPad game, this is just my learning Unity project. The game i have in mind is like Command and Conquer for iPhone well my question is what kind of texture resolution should I be using? I am making a buildings and I want to have lots of them. Right now im making texture size at 256x256 is it too small for iPhone 4 and iPad?
building size is going to be same size as in C&C not going to see them up close.

Thanks

Stan

Texturesizes can be easily determined by thinking.

You can take your screen resolution and then the maximal size of the object on this resolution. So you can calculate the number of pixels the object takes on screen. So your texture has to span this size, just make it a nice power of 2 format and you are done.

Your textures all need to be square powers of 8, so 2x2, 4x4, 8x8, 16x16, 32x32, 64x64… 1024x1024.

I think Unity 3 and the high-end iDevices (iPhone 4, iPhone 3GS and iPad) all support 2048x2048 textures now too. Can anyone confirm this?