Hard to tell... It depends how you feel about it, making 1 big file makes coding more troublesome plus you need to test how it display on all browsers. The most important I would say is your personal preference. These are just simple small tiles, it will work fine both ways.
It also depends on number of tiles. If there is only 100 then one bigger file sounds perfect. But one file with 1000 sounds too big, plus most of these won't be needed in most cases, so a wasteful slowdown to load it. With 1000 I would go for separate files.