What do you mean by "backgrounds of such size"? If you're referring to how small the knight is relative to the screen, that depends on the type of game this is, and the camera motion.
The bricks read fine, though I think they'd look a lot better if they were bigger.
The knight doesn't look finished. It looks like they're wearing grey spandex rather than metal armour. The armour needs more sections. Shoulder guards, knee guards, etc. In addition, armour is shiny (high-contrast) and tends to reflects the colours around it rather than just being pure grey.
