While I take your point and agree that they probably would look nice and break up the text, if they're only there to make the chapter more interesting [looking] I would imagine your supv would veto them. It's a big 'no no' to have graphs or figures or tables without referring to them in the text; otherwise they're just padding. The same applies, I feel to photos. Unless they're integral to the text, I don't think they should be included.
If you can find a way to refer to them and justify their inclusion, go for it (up)