1. Global Illumination- Having all light and lighting sources based off this principle. I believe UMBRA provides an excellent example of how Global Illumination works.
2. Shadows- Having Dynamic static shadows is a must! Oblivion's E3 demo had them, why take them out for Skyrim?
3. Atmospheric Scattering/Dynamic Sky planes- Maybe something along the lines of Red Dead Redemption's sky boxes?
4. Reintroduce Bump Maps/Environment mapping- Morrowind had both and Fallout only had Bump Mapping. Skyrim needs them!
5. A new Fog system- Oblivion's Fog looked like a large wall just coming at you. Fog in real life does not look anything like that.
6. Performance Friendly SSAO- Fallout 3 was able to make use of this through the graphics card display settings.
7. Weather Effects
8. DX11 Support
9. Realistic Water System
Just a few of the many ideas out there. What are some of your graphic wishlists?