Research & Development
Creative Art
Lighting is nice with strong color along with dust particles.
I'd suggest taking reference images of Skipton castle courtyard and breaking down different parts of the images. How are the actual things constructed? How do your meshes compare?
A nice practice might be to steer clear of the textures a bit, and work on the silhouettes of objects and make them look closer and more interesting to how they look in the reference images before going into the texturing parts. After getting the roundness and such looking similar, you could start going into the unwrapping stages and figuring how to get certain texel densities. 512 or 1024 texel density is good for today's video games. From there, you can calculate how many tiles you should have in your texture maps (2k map with 1k texel density means, that the texture would cover 2x2 meters of a wall.)
After these, you could start expanding your knowledge. For example, you can have a look at other people's submissions on this page - you can learn a lot with an open mindset.
I'd steer a bit clear of the ZBrush at this point, you can add a lot more interest into the scenes by adding meaningful polygons.
(Food for thought; In triple-A production the first steps are to make the areas feel nice and good. This is referred to as whiteboxing phase, due to how it looks; there are no textures and the player path, guidance, sense of space etc. are in the key focus. From there, when it starts to feel good, you start adding more interest to the meshes; this is referred to as a greyboxing phase, where the meshes start to look more intriguing and bigger chunks are broken down to modules. Afterwards comes alpha, beta and polish during which you add textures, sculpted additions, vertex blending, decals and other polish.)
Technical Art
The assets are a bit on the low end. Tileable textures are used well in the scene. Scales of things could benefit from extra minutes of Googling for asset dimensions.
Documentation
The documentation is clear to read in a text format. Images and progress shots with thoughts behind reference and mood boards would have been a nice addition.
Final Presentation
The Crest shot looks very nice, and the shapes and forms are easily distinguishable.