mores

MetaBackGround will let you specify a post background by adding a custom field. This is not the sorcerer’s stone, but some users are not comfortable with php and editing of theme files, so all they need to do is install this plugin.

MetaBackGround

I once created this plugin for someone ... they needed to set backgrounds on a per-post basis.

Ciprian Turcu

widget that you can place in your sidebar and that will show the blogger current mood by selecting one of the 12(so far) emoticons available. 
You can select 4 different sizes, depending on the size in width of your sidebar(so it fits just right).
Update 1.1: 4 more emoticons added 
Update 1.2: Dynamic Title(changeable from widget page) 
Update 1.2.1: Fixed a small design issue and aligned mood icon to center 
Update 1.0.1 Small other important design issue 
Update 1.2.3 Small admin_menu fix for wp 2.8.1 
DONATE! <a href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=8322585" rel="nofollow ugc">DONATE HERE</a> – (any ammount using paypal or credit card)

Mood Personalizer

Widget that you can place in your sidebar and show your current mood.

MetaBackGround vs Mood Personalizer