Well, the Kindle Touch and I think the rest of the newer models store them in
Code:
/mnt/us/screenshot_{YYYY}_{MM}_{DD}T{HH}_{MM}_{SS}.png
I use mv /mnt/us/screenshot*.png /mnt/us/images/ to move them to the new location for the now well-hidden image viewer (requires Collections Manager to unhide, is Collection at the very end of library list).
Yeah, the wildcard works fine.