It's nice to see something for viola (my main instrument is the viola and it's hard to find good show pieces sometimes).
I feel that, overall, your piece is great for a first work, although it tended to lack melody in many parts (melody is something I'm a bit of a stickler about). Other than melody, your piece had no real major problems.
The minor problems (in my opinion) are that the piece sometimes wandered away from Baroque style (which isn't altogether a bad thing) and that some of the chords are... awkward.
For example, in measure 19 of the first movement, the two triple stops are a bit annoying to play and might not yield the same quality as having just the sixth (just the A and the higher F). Another example is the chord in measure 5 of the third movement, where it would be impossible to play without breaking the chord, which usually doesn't sound as good as it would if you were to change the low A to a D so that the chord was F, D, A, F (reading bottom-to-top). Weird chords, although being more technically difficult, aren't worth it because they tend to sound worse and much of the audience wouldn't notice the slight change in the chord it would require to make it easier to play.
The last thing I noticed was that there seemed to be a bit too much jumping from the high register to the low register (and vice versa) for my taste.
For example, in measures 13-14, the phrase ends an octave below where most of the phrase was situated. In this case, I would suggest moving the A up an octave. (Maybe it's just me, but it sounds odd.)
Just for a few good reference pieces for viola, I would look at...
Hoffmiester Viola Concerto in D (especially the 1st mvmt):
YouTube - Beijing viola competition??hoffmeister 1rd mov
Telemann Viola Concerto in G:
Reger Viola Suite, 4th mvmt (maybe: it is far removed from Baroque...):
Anyways... I think the piece is good and it is great to see something for viola. :D