There is an option in Gallery that you can set a specific image to the category, the album or both image.

This is a great feature however if you want to reset the image to be the most recent image again there is no way to do this. Both om the album and category level. The only way to change out the image at this point is to set a new image as the category/album image. While this is great if you want to feature a specific image for every category however if you are messing around or testing things this is a permanent change. The only way I know of to fix this is to create a new category and move all of the images and albums to that category however that doesn't fix the album image.

 

Basically the tl;dr version is a reset to the gallery image for categories and albums.

I agree.