If you are like me, you have a little system to keep pictures and wallpapers synced with your iPod/iPhone.
In iPhoto, I kept an album of all my iPhone wallpapers that I synced through iTunes. That worked great for a year, but since last week I’m trying out Aperture and I came across a small problem with my wallpapers where their resolution is awful once synced to the iPhone.

When syncing from an Aperture Library you actually only sync the previews of you pictures. By default, Aperture creates previews at 1/2 the resolution of the original files for saving space and processing time. This is usefull for hi-res pictures, but bad for the iPhone Wallpapers because they are at the exact resolution of the iPhone screen. The quick and easy solution is to:
1. change the preferences of Aperture’s Limit preview size to Don’t Limit.

2. regenerate the previews by selecting all pictures in the album, right-click and Update Previews

3. Re-sync the album to the iPhone through iTunes.
I suggest you set your Aperture’s preferences back to the original settings if you want Aperture to create small previews that are actually useful for hi-res pictures. If you keep the Don’t limit option, your library will likely double its size over time (originals + full-res previews)
And again, you can find the best iPhone wallpapers at Poolga.com.