This is a perspective issue really. Going straight down, no walls, type of look will probably be a bit hard to portray a wall like that. I think if I was going to do it, I would try to put something on top of the wall to dictate the size disparity and thus force the perspective a bit. You could also extend the shadow farther to give it a taller perspective, and you could play with that to help give the land some additional depth as well.
Quick side note, for your training yard, the two main ways to practice will be pairing up and pell work. Considering this used to house many people, with an avid recruiting plan that would make many a military jealous, I would recommend giving it more space and create a condensed area of pells. Make sure to give a solid 6-foot minimum about the pells as well, I speak from experience with that one. Unless your people are fighting like fencers, they're going to take up a lot of room with a minimum of 3-feet if they only stand in front of it and do little footwork(a key factor in sword fighting). Add to that, it's referenced that they had a penchant for longswords(also known as the bastard sword) which is a hand-and-a-half sword(can be used in one, or two, hands). For a rough estimate on their length from pommel to tip, it would be from the ground to about elbow level(quick side note, as if I haven't already gone on a tangent, well made longswords weigh about 2lbs 8 ounces).