I have been using MC for Audio for years, but I only just started using it for Photos / Images. And I am making good progress in using MC to organize my photo library into albums, and adding tags for people and places etc. And obviously MC is great in TheaterView for browsing for my images, filtered according album, date, tags etc.
But one thing that I sorely miss is an Images > Library Tools > Convert Format feature. In Audio and Video, you have the ability to convert media to other formats for use on (say) other devices. And it would be great to have the same feature for Images too. For example it is good to have the original RAW images displayed in MC, and it would be good to have an option convert them to JPG or PNG for forward to friends by email or social media.
For example Images > Library Tools > Convert Format for JPG would have (say) options for Destination Compression, and Destination Image size; allowing a large RAW file to be converted to a small JPG. Ditto for PNG.
Note that the MC DLNA server does already have the capability to convert Images to different sizes of JPEG, so I think it should be relatively easy to use the same engine for Images > Library Tools > Convert Format as well.
PS a further "icing on the cake" would be a right click context menu for Share via | eMail | Facebook | Twitter | etc.