Yeah, I'm trying that too but there seems to be a bug. You can set the two different sizes, but it will only load the size for the thing you are currently at.

Right now I have a big album art for portrait and smaller for landscape. If I am at landscape and a new song comes up, the album is loaded with the small size. I flip to portrait and it stays with the small size so there's a gap. Now if a new song comes then it loads the big size, so if I flip back to landscape it gets clipped. The widget should load both sizes automatically and display appropriately.