In the near future, wallpapers in the gallery will be categorized according to dimensions.
How to find out which wallpapers fit your phone:
1. Look for screen size/resolution (px) in your user manual. Most of the time, there is a page at the back with a list of specification for your phone.
If not, you can look for product specification online.
Go to GsmArena, look for the manufacturer of your phone. Then, select the model of your phone. Under display > size you can see numbers in pixels. For example, with Nokia N95, the screen size is 240 x 320 pixels.
2. Download wallpapers of the correct dimension.
128 X 128 Wallpapers
128 X 160 Wallpapers
208 X 208 Wallpapers
176 X 208 Wallpapers
176 X 220 Wallpapers
240 X 260 Wallpapers
240 X 320 Wallpapers
320 X 240 Wallpapers
352 X 416 Wallpapers