Most are helm's words.
Beware the workings of the Beast for they manifest through the man that will go by the name of head protection apparatus [Rev 14:8]
I'll let Adarias explain what he ment from asking you to unify the palette, but since I was summoned thusly, I might as well give you more critique:
There's odd mirroring that doesn't serve a clear purpose other than finishing sooner. Highlights are mirrored along with shapes, suggesting not a clear lightsource. The foreground brown building is done much more sketchily than the buildings in the back (whom I like most about this) and the monochromaticim makes it look as if it's made from delicious chocolate. You're using few shades, but the placement of the pixels is not attentive enough to make up for it, therefore you're left with a kind of oekaki-style thing that I can't tell you how to make better without suggesting either more colors and detail in texturing, or just extremely clearer lineart. More attention should be paid to how light would effect the scene, and finally if this is for a website, a mockup where it's integrated should be done at some point just to see how it would all work in whole. Avoid programmer pink when you can put it on transparent, no?