I would love to try a portrait of a dog. However, I'm not the best when it comes to fur/hair.
About the dog picture, everything looks okay except for the nails of the dog looks a little rushed, and the ground looks a little bit uneven.

When you're trying to do lines to create a more perfect box/square you can use focal points either on the paper, or off of it and use a ruler to make sure the line is straight.

If you do it, you can get the proportion nearly dead on accurate when it comes to 3D-ish look.

EDIT: It actually looks like you tried a two focal point method for it, but idk it seems like maybe it's a bit off still. :s