caller pictures for Nokia 2700

please can anybody tell me how to get large caller pix (i.e. pix that i have saved in my contacts and when the caller calls me then i get small pix of the caller, but in case of my other Nokia 2700 cell phone the caller images are large)
please if anybody knows how to change the size of the images saved in the contacts of any series 40 cell phone please help.

i would use IrfanView on ur computer to match the size of your screen. then put it on ur phone