I'm going to give this one last go, step by step:
1. Your background pack will be either a zip or a rar file. Decompress (unzip) it. Windows XP can unzip .zip files, WinRAR will decompress rar files.
2. You should now have a folder containing a lot of background files (pictures) and a file called config.xml
3. Move all of these files (pictures and the config.xml) to "C

Program Files\Sports Interactive\Football Manager 2006\data\graphics\backgrounds", not a shortcut, move the actual files.
4. Load FM, make sure the 'skin cache' option in preferences is unticked. Close FM.
5. Reload FM. Your backgrounds should now be showing for the teams you downloaded them for.
You cannot have pictures during a match day - only backgrounds for a team.
I've set that out as simply as possible. If you don't know how to do any of those steps then I doubt anyone can help you - it is all simple copy and pasting.