Well, I don't have much experience with bloodtrailing dogs, but dogs in general, well, that's what I do for a living.
I own & operate aboarding kennel & dog grooming parlor (salon sounds
soooo gay!) & I've been bitten by more Dachshunds than any other dog. It seems like 9 out of 10 are pure-bred bastards & the other 1 is half-bred bastard/retard.
Something to bear in mind, you're really not going to spend much time actually working a tracking dog, unlike a pointer or flushing dog, so choose a breed that makes for a good companion. If you prefer a smaller breed, a small Rat Terrier/Jack Russel - Chihuahua cross would make an excellent companion with a fantastic nose. Pretty much any dog can be trained to trail, if you start it young enough (personally I'd want to get it on blood no later than 6 months) & generall speaking Mutts make the best natured, least neurotic dogs. There are so many problems associated with all pedigree dogs that a little cross-breeding can really help a dog out. The little Jack Russel/Chihuahua crosses often misrepresented as Rat Terriers are, generally, the friendliest, easiest to train dogs I've ever come across that aren't Hounds.
A small bodied Beagle would also be a great choice, but they do need a lot of stimulation. They absolutely crave to work, otherwise they'll run to fat, but if they're well exercised, they are a pure joy to be around!
This is Tremble, my Jack/Chi cross. Friendliest, smartest little critter I've ever come across! Her personality fills the entire room!
Oh, this is her usual position whenever I'm reading. She's very 'anti-literature'