It uses computer numbers, e.g there are 1024 mb in a gigabyte; different mb's of RAM you can get etc.
All numbers in this sequence work, if you understand :D
examples:
It depends on how good you want the quality, i.e 64x64 won't give good quality, but will load really fast, and 2048x2048 will give excellent quality but will lag lots.
As long as the picture is one of the above measurements, the printbrick will resize 64 squared (however many times needed) to fit on the brick.
English: As long as it is one of the above, it will work. If it isn't, it won't work, it as counted as an invalid size, and won't display properly on the print brick.
