"Haloing Thor" means that Thor is placing a halo on someone because the participle "haloing" describes what Thor is doing. A "nursing mother" is not getting milk from her infant, but giving milk to her infant.
A "haloed Thor" means that someone or something has placed a halo around Thor's head just as a "burned building" means that someone or something has burned the building. It describes what has happened to Thor.
The question of which is more common is much more difficult. Common among whom?
I do not know what cultures have portrayed divinities and the divinely blessed with a halo. (The first that I am aware that did this was the Byzantine culture, but they may have imported it from elsewhere such as Persia or Syria.) Nothing I know even suggests that haloes were a "thing" in Nordic religion although I have some recollection that early Indo-European divinities were generally considered "bright." Of course, the great majority of readers of comic books have no inkling of the traditional iconography of Nordic or any other religion. You can say that the Buddha was Thor's mother, and virtually no one who reads graphic novels will even blink.
The issue of how common is the idea of Thor bestowing haloes or having one bestowed on Him is an esoteric question that may require the combined erudition of those who study comparative Indo-European mythology and those who study iconography.