People can argue all day about "what is art?", but to me, it's something that provokes thoughtfulness or a sense of wonder. Something that communicates a view of the world. And I think this [ http://hallasko.com/collections/prints/products/looking-up ] and this [ http://hallasko.com/collections/prints/products/aglowfish ] easily meet that condition, while also exploring what can be done in the medium.
Yeah, we're talking about that they were made in Paint, because he's showing us a painter[2] can do with Paint. If you ask me, that's valuable.
[1] http://en.wikipedia.org/wiki/Constrained_writing
[2] He has a lot of experience as an actual painter, too, which means he's a lot more qualified than I am to decide something's artistically valuable.