What's the largest size of your image files?
-> 417 x 479
1353x793x4=4291716 bytes = 4,3 Mb in active memory if it's not placed on a power of 2 plate in which case it would be 2048x2048x4= 16,8 Mb in active memory.
Large images can be a performance killer..
Although ofcourse it's not the only factor..
It is not necessary to put the sprite on a power of 2 ? Just the imported image ?
And what are the other factors?