If it's a desktop, report it. Don't bother tagging it, I'll know if it's a desktop.
If it's a screenshot of something like a browser or not wallpaper related, click report.
If you don't know what it is, don't tag it.
If you know what it is, tag it with words that you would use to find that image. Seperate multiple tags with a comma (e.g. rain, beach).
Image InformationResolution:1024x768 Board:wg Poster's Name:Anonymous Poster's Tripcode: Downloads:398 Date Added:2009-11-11 00:00:00 SFW:Safe For Work