What device are you using?
I'm using a Samsung Galaxy Tab 10.1.
I found that after putting photos on the tab, I sometimes have to reboot it
for PS Touch to "see" them.
So, try rebooting your device if you haven't already.
Hi, this sounds like an issue that has been mentioned in this thread:
The workaround is
It will now rescan all your data on the device so it might take a while before the images are visible in PS Touch.