On the map of Skyrim that has been circulating (and which I'm probably not allowed to link to) you can clearly see numerous small red crosses dotted all around the map on small Islands, atop mountains, at the bottom of lakes and sat out in the middle of nowhere. According to my counting there are 24 in all which ruled out my initial thought that they might be daedric shines (although thinking about it there may just be more than one of each). What else could they be?
EDIT:
My thoughts: - Just plain old 'treasure island'-style treasure/loot
- Dwarven artefacts/ruins
- Ancient shines of some sort
- Bits or ancient ruin similar to the mossy head that was seen in the trailer.
- Imperial forts or encampments
- Some sort of cult shines
Etc. etc. etc.....