Loose gave us TRO-3057, a book I love above all other TROs. I know you mean your words in jest and don't actually dislike his art, but on some backwater planets insulting the illustrator of the Clan refit Lola III could get you airlocked, or tied to a jumpsail tether and left floating in space for a full KF drive charge. #P
If you want to talk about ugly art (everything from Dark Ages notwithstanding), over half of everything in TRO-3055 original, the Mackie, and the Blitzkrieg/Yeoman abominations of 3060 (seriously, armless mecha belong in Starsiege, not Battletech).