Links to free-for-use guitar related graphics that you can put on your personal website can be found here: http://guitar.about.com/msub28.htm

For Example:

Music Graphics Galore
http://www.geocities.com/Nashville/Opry/1809/graphics-3.html#Electric
This giant archive has over 175 pics of electric and acoustic guitars, divided into small, large, and animated categories.

Orchid's Free Music Clipart
http://www.magicnet.net/~orchid/Music.htm
One medium-sized generic acoustic guitar illustration, and one Fender-style electric bass on this site. Read "Instructions" for terms of use.