Is my boy Sheltie or Aussie mix?

I have to say...he looks an aussie in a sheltie body. He's got the aussie markings, but not as solid as an aussie.
 
Maybe he's just a sheltie w/ improper tail carriage? Naw, prolly not. [8|]

I'd say "mini Aussie" (I use the term loosely). There's lots of breeders that are doing silly things as a shortcut to the small size - including various crosses. Cute as a button, though - and I bet you two could have fun in flyball and agility. []

Since he came from a shelter in upper SC  from an area which is notorious for puppy mills, it's quite possible, and I think even likely, he's some  back yard breeder or puppy miller's attempt at crossing an aussie with a smaller breed to get the "mini" aussie.  I think his coat may not be going to get as fluffy as some aussie's or shelties, which is fine with me, he's a love no matter what breed he is.  So he will have a "working" coat I guess. [] then again, that coat may fool me and be all fluffy next spring. Sometimes it takes a while for the coat to "come back"
 
As far as him getting into agility, I don't think he'd ever be a real contender in trials. Before he arrived at the shelter, some "lovely" [:'(] erson decided to shoot at him with a pellet gun. Damged his back left leg. Was never taken to the vet, and it healed improperly. As a result he favors the leg and will not put weight on it,  he just carries it limp 90 % of the time. But he doesn't let that slow him down much.  If he enjoyed playing around on some of the agility equipment, I'd do it for his pleasure and the interaction.
 
 

He may well be a mix, but he could be a purebred, too - working Aussies are not large - 18-20' at the shoulder, and 30-45 pounds.  The ears say Aussie, and so does the coat - working dogs, which might easily be found in SC, are not always "typey" (after all, if they can move cows, they don't have to be) have a moderate coat, not at all the same as the show dogs one finds with the huge bone and copious coats.
What does his personality say?  Is he "busy"?

By the way, Aussies talk back, too.  And, their welcome barks can sound like a pack of coyotes LOL.

hello spiritdogs. My lil buddy is about17-20 lbs and not very big at all. he is quite talkative and roo roos  a lot. when he's feeling playful, he's full of energy and hop-runs pretty fast (hops due to the permanent injury) loves his squeak toy. But he also can settle down pretty fast and loves to cuddle ( and mom loves that too! lol) he seems content to have his mom and his doggy and kitty friends around.  and his ears.....oh my how cute are those ears. he just sits and looks up at me and I talk to him and those ears move around like a bat, they tip then they stick straight up, he's quite entertaining.
 
gee, you'd never know I'm crazy about him would you? lol.