Android - Unwanted folders showing up in Gallery. Can they be removed?

Yes you can! In directories that you do not want scanned by the media scanner put a blank file called .nomedia

Don't forget the "."

Windows may not let you create this file because of the name.

Some file explorer apps have an option for creating this file.

The app developers should have created this file for you but some forget.

.nomedia doesn't solve the problem at all! Putting that file in folder where you store music (to get rid of all covers to be listed in gallery) also excludes all the music in the media player (PlayerPro in my case).

I would suggest using a BETTER gallery, like QuickPic, where you can set which folder to INCLUDE instead of needing to exclude folders. I Still don't get it why this option isn't available in stock gallery!

Another solution would be to use a separate app to HIDE certain folders, if your issue is that you have some 'secret' folders you don't want your friends or gf/bf to see ;) Hideit Pro is an excellent app of that kind.