More details, including a full-resolution image, are at http://eccssw.com/astro/Artifacts/. A close-up of four of the colored artifacts and a star spike is below.
They are reflections from a bright star near the field, probably a star just outside the visible field. The light is bouncing off of something in the optical train. The reflections appear in slightly different places because the telescope was positioned slightly differently for each shot. As for the spikes, these stars are very oversaturated, so it wouldn't take much to show a faint spike. I looked through my collection and can see similar spikes in images I've taken with a couple of different cameras. I'm thinking it's a little bit of scattered light from the microlenses on the CCD array.
