Useful Link
The following links mostly contain UO artwork though some of them are good resources for programs.
http://www.uo-pixel.de
http://nyray.wordpress.com
http://isispixel.wordpress.com
http://runuo.uodev.de
http://uo.dunkelraum.net
http://www.darkshard.net
http://www.uo-stuff.de/uo-stuff
http://ultimaonlinegumpart.tk
http://www.ryandor.com
http://vestimisu.blogspot.com