Im going to show you two of the great skin edits going. They have been going around for a while, the first one is skin edit pre alpha. This program is old and doesnt get updated anymore but nether the less it is still a great program. easy to use and learn. The other is MCskinedit 3d, its identical to Skin edit pre alpha but has the choice to add mobs, more 3d like and a bit more options.

Download links.

Pre alpha: www.moddb.com/games/minecraft/downloads/skinedit-alpha-3-pre-5
MCskin 3d: (Ad link removed)