Improvement for Mashtape: Use Album Artist instead of Artist to get metadata

Hi, I'd like to suggest something that other people also might like:

I'd like to be able to select if Mashtape uses Artist or Album Artist in order to get the info from last.fm etc. (or put in a preference order...).
There's many duets or other songs with artists featuring other artists and for those constellations last.fm rarely has an entry big enough to find pictures for the flickr slideshow etc...

Think about it, shouldn't be too much of an effort to implement this change (i think?)...