Need help ps3 themes?

can someone help me wit this i did wat some site told me to do but my ps3 wont read the themes i have saved on my usb can someone tell me y and theres one more thing when i tried to look at the theme that was dl it didnt show me the pic and pop up wat program to use and i tried paint and i have a feeling i mess up by doin that so if u can plz hlp me out