Given that the difference between what is considered small, average and large is relatively small - usually 1-2 inches or thereabouts, it's very difficult to say for sure from photgraphs like this with no frame of reference with which to judge absolute size from relative size.
If I had to guess, I'd say he is around 6"NBP in length and between 4.5 and 5"" around. Therefore he's noticeably above average in length and average girth, in which case he's on the large side overall.