Oh God! Did I do a booboo!

A few years ago, I was looking for a way to hang pictures on some
walls in such a way that they would not 'move'. That is, hanging them
from a single, center hook would allow them to continually require
adjusting to make the straight all the time.

I opted to use some velcro thingees I found at HD which were
recommended and which did the job seemingly. The thingees were
velcro'ed on one side and gummy (sticky) on the other side. The trick
was to stick one velcro piece on the wall, and the velcro matching
piece on the picture. Then when you press them together they not only
hold the picture but they hold the picture very firmly. It worked!

Now I want to re-paint. Guess what? The velcro pieces on the wall
left a gummy, sticky residue on the wall that I dare not try to simply
paint over, and which I cannot remove very well. I have tried
acetone, paint thinner, sandpaper. A scraper merely moves the
residue around.

Is there another solvent I should try? Any other ideas?

Thanks

Geezer