The perspective on the house is messed up.
You used a brush preset to do the leaves and at least part of the grass- something I've tried in the past but I find it just makes everything look like a Bryce 3D model.
The thatching didn't turn out very well, and it overlaps the tree trunk in the foreground. While you have a good command of lighting (particularly on the surface of the house) you need to work on your textures. The tree trunks don't look like bark. Some of the shading work on the structure of the house is bleeding over onto the windows and door.
Fixing the sun would be easy, it's just a matter of throwing some crafty lighting filters on the background layer. Assuming, of course, that you didn't just paint this all on one layer in Photoshop. There should be light bleeding through the gaps in the leaves. You did some highlighting on the left-hand tree, which is nice, but it's getting overwhelmed by all that flat green.
The shadow on the lefthand tree is pointing the wrong way.
The shading on the house would seem to indicate a light source behind and to the left of the point-of-view, not the sun in the back of the house.
From a compositional point of view, that tree on the right is totally overwhelming the rest of the painting. I'm interested in looking at the big bright white house in the middle of the piece, not the huge blob of solid green leaves covering the top 1/5th of the painting, but those leaves effectively crop out that part of the picture. It doesn't look to me like you were interested in painting the tree so much as obscuring the top of the house.
The painting needs more balance- you've got these big chunks of color all grouped into blobs around the "canvas" like kids at a middle school dance. Mix them up! Pull some of the lighter tones from the house into highlights on the leaves- which, again, shouldn't have been a brush preset if you're going for "fine art", which I'm assuming you were since this is a final project. Take the time and at least do some Impressionistic paint daubs or pointillism or SOMETHING* more interesting to look at. Use more than three shades of green for the foliage- the shrubs probably wouldn't be the same color as the deciduous trees above them. This isn't background art for a comic strip or something meant to compress down into a 256-color PNG file. There's no justification for limiting your pallette in that area. The semi-opaque, blurry leaves in front of the sun look really crappy.
*My current favorite foliage trick is to take an oval or similarly irregularly-shaped brush, crank up the "scatter" setting, and lay down tons and tons of widely dispersed dots. On small scales (ie the size of one of my panels) it pulls of a fairly decent foliage facsimile if you're crafty with the shading.