Generally it should look quite different from modern UI principles (they're quite bad anyways). I'm thinking of mainly getting inspired by old symbian mobile phones with a dash of iPod and some GameBoy Advance/PS2 with some Windows 2000. So a huge retro mix. Though on a practical note I'll have to mostly look at mobile phones since the resolution is quite limiting and they generally do quite well.
Font
Definitely need a raster font, probably gonna start with the Unifont though a smaller font might be worthwhile since 8x16 is rather big. Unifont is nice though since it'd allow for supporting many more languages, don't need full unicode support but supporting at least common European/Asian languages would be quite nice.