Using any background picture for your desktop that is fewer pixels that your set resolution is going show edges of the background desktop around the edges, if your Desktop background setting is set to "Center" (vs "Tile" or "Stretch").
You said your set resolution is over 2000. If that is true, then you will need pictures at least as large to not have the bare desktop background not show.
None of the default desktop background pictures in Vista have that high of a resolution. But it is not that hard to increase the number of pixels of any your desired pictures (with a corresponding loss of some clarity - but it may be acceptable).
I am somewhat confused, by your wording, as to what you want to have.
If you want the current pictures to fill your desktop, just use "Stretch"
If you want some edge to show, use "Center"
If you want less edge to show, use larger pictures and "Center"
Finally, if you want some edge to show BUT perhaps not equal amounts around the picture (such as if you want the picture to be in the upper right corner, and an edge to be on the left and/or bottom) there are entries to put in your registry to offset the "Center" picture.
(I do that on some of my computers, since WinXP doesn't have easy ways of doing that trick. I do not know if Vista has an easy way of adjusting the offset.)