Here's a nice demoness character with red skin, horns and tail.   http://www.runtimedna.com/Jezebeth.html   There are also several horn props here in Freestuff.   A quick search turned these up:  http://www.renderosity.com/mod/freestuff/search.php?section_id=-1&query=horns&sort=relevancy&use_age=no&older_age=&older_units=day&newer_age=&newer_units=day&username=&section_selector%5B0%5D=-1   I personally like nfredman's Oni horns but that's a matter of taste :)