File size has little or nothing to do with getting wallpaper to appear correctly - at least on my EE. The main requirement is the pixel vertical and horizontal resolution.
The wallpaper I use on the LCD is a larger picture resized to 1024 x 600 and the e-ink was resized to 1200 x 800 - the EE enlarged that to 1200 x 825 with little discernible distortion.
There are several programs that will allow you to resize pictures while keeping the aspect ratio. You may have to go to a slightly larger size and crop, or let your PE do the final sizing for you.
This assumes you know the actual sizes of the screens on your PE.
|