I would describe him as a blue mackerel tabby and white domestic shorthair. I'm not personally seeing any influence of any specific breeds. Most cats are not any particular breed.
His legs are not short enough for him to be a short-legged Munchkin. I think they just look short because his belly is a bit tubby. If he lost some weight he would have normal proportions for a domestic cat.
abyeb
, I think you are seeing him as a solid blue because because it is a somewhat unclear picture, he is a dark tabby, and his white markings are covering up most of the lighter areas in his tabby pattern. However, an adult cat will not normally have prominent ghost markings. You also can tell from looking at his nose that he is a tabby cat (the nose leather is lighter in the middle and outlined with a darker color). You can also see the beige ground color on his whisker pads and on the front of his rear hind leg.