What Kind of Dog Do I have?

and more pictures:

Sounds crazy, but I see Shih Tzu.  His ears are the right shape, body style is right.  That would also explain his shortened muzzle.  So, my guess will be Shih Tzu/Lab.

My guess it pug/beagle (which are now bred on purpose and called "puggles" [&o]).
 
I really don't mean to pick on you or your dog, but he appears to be a bit overweight, which is really hard on their joints, heart, lungs, and pretty much everything else. We all know that being overweight is bad for people, so think about if we aged 7 times faster than we do. I think of it like it's 7 times worse for dogs to be overweight than for people, and it's pretty bad for people.

I've never heard anyone say he's overweight at all.  Every vet has said hes at a good weight.

I think the legs are too short for a pug/beagle cross.  I agree he might be a tad overweight.  Not horribly though!  When you look down on him from above, he should have a noticable waist.  He looks like a sweetie though!  I especially like the second picture!  He looks so innocent.

I've never heard anyone say he's overweight at all.

It's hard to tell from pictures, so I could be wrong. It just looked that way to me, but I can understand if he's not. My dog sometimes looks a bit chubby in pictures, and she's not at all. He should have easily felt ribs, and like Colleen said, a noticeable waist. If he does, I apologize for saying he looks overweight.
 

I think the legs are too short for a pug/beagle cross. 

 
Oh yeah, I didn't even think about that. Now I think corgi/pug. []

Seeing that coloring and the ears, I have no doubt that there is Lab in there.  Everything about the posture, leg shape/positioning/muzzle length/eye placement/ear size just SCREAMS Shih Tzu to me...though I can't for the life of me imagine a Lab pairing with a Shih Tzu.
 
And for the record, I don't think he looks that overweight.  Maybe by a few pounds, but I think a lot of it has to do with body type.  I have a Lab/Basset X and have the hardest time telling if he's overweight or not because he just NEVER has a tummy tuck up at all.  I feel like I should be able to see his stomach visibly tucking up from the side, but it just doesn't at all.  He looks like a sausage, especially when he sits down like the OP's dog does...his tummy bunches up and makes him look extra tubby.  I wish he would look nice and slender and healthy, but the truth is his body just isn't shaped that way.  It's especially apparent if he hasn't...err...number 2ed yet - he looks very noticeably more slender after he does [&:]
 

I'm glad I'm not the only one who sees Shih Tzu!!! 
A better way then relying on the "tuck-up" is to look from above for a waist and feeling of ribs.  You should be able to slightly feel the ribs when you run your hand down the dogs side.  You should also see a bit of a waist before the hips when you look from above.  I agree it's hard to tell from pictures, but it was just a suggestion.  Excess weight is especially hard on long backed dogs because it pulls down on their spine.  You can judge much better since you are with the dog!

I say pug/corgi. My girl always sits like that.

First thing I saw was pug because of the shorter muzzle and the overall color of his body. That could also explain the little bit of cubbyness that he has. I'm also thinking maybe some basset hound for the size and thoes legs. My best guess would be pug/basset with something else in there I can't quite place.

There is no blood test that can tell you the exact breed or mixes of breeds he is but there are test that can be done to give you an idea of helth concerns that may be breed specific. You could have blood test done to check out his overall health, especialy if your concerned about his weight. Many times it's not the owners falult for the dog being a little heavy, they may have a problem like being hypothyroid. Hypothyroidism is a breed specific problem so if he is then you could narrow your breeds to only thoes who are pron to that problem such as labs, cockers, rotties. I don't want to scare you by saying he could be hypothyroid but i was only using that as an examole to show how a blood test can be used to get an idea of what breed he is but still not exact. Basicaly unless there is something wrong with his blood test then there is no way to know using any type of blood screaning. If he is an overall healthy dog then I would not worrie about blood test untill he is around 7 years old.