I have been wondering if you could take slightly out of focus photos and turn then into sharper images. I know from recently looking at old family photos that plenty of them suffer from being taken on cameras with bad quality focus and are only just out of focus. It seems that this should be reasonably easy to make datasets by adding some blur etc.
This (and denoising + SR) could also be really interesting to apply to audio to get clearer audio for phones and hearing aids etc.