Best use of textures dealing with iOS, GUI.DrawTexture, and everything else

Unity Engine
,
1

I’m working on an app that uses a lot of images. The images I have now are all 640x960. These images will be called by the GUI.DrawTexture script. The settings I have applied to them are as follow:

Aniso Level = 1
Filter Mode = Bilinear
Wrap Mode = Clamp
Texture Type = GUI
Override for iPhone = true
Max Size = 1024
Format = Truecolor

I really am no master to textures and how to properly use them. Should all of these be perfect squares? These setting look wonderful on my iPhone 4, is it going to kill me as my app grows?

This app is mostly relying on GUI elements btw.

2

This is inevitably a trade-off between the size of the resulting app and the quality of the images. If those textures are all used as background images then the large image size may be justified. However, if they will be displayed at less than the full screen size (images for buttons, say) then the high resolution will not achieve anything. There is no need to have a texture at anything greater than its final display size on the highest resolution device (which may be the iPhone 4 or iPad, depending on what you are doing).