weird icons showing up on photo slideshow in sleep mode, please help

[cajunbymarriage]

When my computer has not been used for awhile, but before blacking out to hibernation, it rolls thru photos we have downloaded on to the computer. It shows each picture for a few seconds than moves to another. However, a few months ago, I noticed that it will display a photo, then instead of moving to another it will display the photo with an generic icon imposed on top of the photo, like a diamond, peace sign, ying-yang symbol, etc, etc. This doesn't happen all the time, but it seems to run thru these like it is another picture. I like the photo display, but want to get rid of the icons showing. Any advice? I am running Mac OS X Version 10.5.8 if that helps. Thank you!