One of the best parts about playing an Engineer is that you get to carry around a rifle. In WAR's 1.3.6 patch a bunch of new rifle models were added to the game. The new rifle models span all of the tiers. With the appearance system, you should be able to use some of these to make your Engineer look even better.
Note: These images are of the base models and not in-game screenshots. They will look similar though.
Sniper's Rifle of Merit (Recruit Emblems)
Sniper's Rifle of Devotion (Scout Emblems)
Unknown Name (Tier 3)
Unknown Name (Tier 3)
Sniper's Rifle of Solemnity (Officer Emblems)
Unknown Name (Tier 4)
Unknown Name (Tier 4)