How to Change Album Art????

So, I had been really happy to get this because you can add in Album Photos! But.. .when I did it it worked BUT the pictures were too small (MY FAULT) BUT the thing is that when I tried to change the photo and get it to change it would say that is saved and I could even see the new picture but when I double click it to open it or even just open it from VLC it comes up as the OLD photo comes up instead of the old that is WAYY to small! So what I am saying is how to change it to a new photo! As I said my music opener is VLC Player the newest version!!~ Please Help! Thanks in Advance!!

how to delet vlc player cache.............
and now explain what the vlc behaviour has to do with mp3tag.