That's gonna be a large desk, lol.
I think individual features depend almost solely on your aesthetic sense and required space.
- I've found in my experience, keyboard trays are more of a hassle than a convience, not only in the building of one, but terms of wear/breaking over time. Most people tend to just leave it extended in practice.
- If your planning on something like your second example (which looks awesome, btw), I would HIGHLY suggest an ultra cheap stainable carboard/particle board backing. It'll save a lot of aggravation of having to climb under your desk to fish out a CD case, pens, food, etc.
I hope that helps and I wish you much luck! As someone who is being pressured to invest in a new desk
(Currently an old sewing table), I'm really interested to see what you come up with.