If you're using getResources then you need to add the includeTVs and processTVs parameters to your getResources call.
Something like this:
[[!getResources? &parents=`id_of_your_resource` &tpl=`chunk_to_handle_templating` &includeTVs=`1` &processTVs=`1`]]
Make sure to prefix your album cover tv with tv in your chunk in order for it to work, so in your chunk you would use
to access your album cover template variable if the TVs name is album_cover.
Now if you are using a gallery TV that might require a bit more work so maybe posting more details on your setup is needed to give you more accurate information.
Good luck.