These are good:
http://twistedsifter.com/2015/03/mind-bending-optical-illusion-paintings-by-rob-gonsalves/
Not so much optical illusions as surrealism (with some inspiration by DalĂ). Very cool indeed.
some are better than others... but a few of them make you double take and are excellent
I skipped a few which didn't seem up to scratch, but enough good ones.