As someone who has not contributed with a skin, my personal opinion is:
1 - I like 2d graphics as opposed 3d buttons and backgrounds on skins. I think this is why jowaldo's skin looks so sharp.
2 - I also like less contrast in colors than more, and would prefer something on the grey side as I am using a RPTV to display Xlobby. I don't really want the red, green or blue gun to run hotter than the other two as it may cause uneven burn-in.
3 - Button highlights are a must for using a remote control
4 - Easily moving back out of a subsection easily wiht a remote is important for me. WIth the default skin, I can't do this in the TV guide. Once I get in that screen I can't get out of the guide matrix to the home button by using the directional arrows. Not sure if that is a skin or Xlobby issue.
5 - My feeling is that vector graphics (gradients for example) look better than photo realistic textures.
6 - A small number of buttons that expand into more options is better than putting all the controls on one page. My feeling is that the default album viewer is too busy and takes a long time to navigate from one side of the screen to the other via remote.
7 - If animations are included (if they can be included) they should occur in response to an action as opposed to happening on a static page as it ends up being distracting. I'm thinking about web pages when I say that, but maybe I just haven't seen this implemented well yet.
I guess that's all I got. I would love to have the time to play around and try to make my own some day. I might become less opinionated then.
THanks,
MR