Choose the current photo or album cover to be the cover of any album in the directory structure, not just the album directly above.
The default album cover selection method in Gallery 3 only allows selection of a gallery cover from one of the images within that level of the gallery. Also, if you put a picture in a gallery temporarily to assign it as an album cover and then remove it, the album cover is removed as well. [Is this correct? I don't think it is. - undagiga] Thus, if you want to assign a gallery cover from a photo in a lower level gallery, you must first assign the photo as the album cover of its parent album, then that album's parent, and so-on, until it reaches the gallery you wanted to cover. Then, if you didn't want that image as the cover for the source gallery, you have to repeat the process to restore the desired album covers to the children galleries.
The Album Cover Browser solves all of this by allowing you to choose any image or album cover as the cover of any other album, even if it's not in the same directory structure. Simply select a thumb that you want to use as the cover for another album, choose "Browse for an album to cover" from the options menu for that thumb, then from the displayed folder tree dialog select the album that the chosen thumb will cover. The only restriction is that you must have edit access to both locations.
Be aware that you use this module by finding the item you want to use as a cover in your gallery, and then apply that to an album you pick from the popup. (That is, you change an album somewhere else in your gallery, not the item you're bringing up the menu for.)