This may not be a logical subject for an art blog, but hear me out. I have been a fan of jigsaw puzzles since I was a kid, and when I came across the Jigsawplanet site, I had found a new way to spend (waste) time on-line. There are probably millions of puzzles there, with a well oiled search engine to find the ones you like. For every puzzle you can choose the level of difficulty (i.e. the number of pieces). I found 140-150 pieces comfortable to play on my 17 inch laptop, both in terms of size and in terms of time required to solve a puzzle (typically 20-30 minutes). So, is there an art angle? There sure is - many famous paintings are available as puzzles on the site. I picked a dozen I recently played as illustration. I had to take the screenshots with the puzzles almost finished, because the finished puzzle automatically converts to the image. Anyway, as the label says: Anything Goes..... The image above is in the public domain.
Copyright statement: low resolution screenshots are deemed fair use; most of these paintings are in the public domain anyway.