If i may suggest - go to Cydia and download the free tweak "iCleaner;" it'll put an icon on your iPad. Open the icon and ensure all the selections are active except "Cydia sources."
Then, at the top, under "Message Attachment," press on the "smart" button; it should highlight. This will ensure that any "stray" pictures from messages (SMS and iMessages) are also cleaned.
Last, press the clean button at the upper right. iCleaner will then do its work and respring.
Hopefully, that'll clear out those pictures. If yes, yay! If not, holler back and we'll take another shot at it.
Marilyn