I agree with DawnBringer. You can probably use even larger tiles than I did, and then you'd have room to add patterns/flowers to some of them like some older bathrooms. I can't find an example of one of those though.

I also think that the dark tiles contrast too much.

The lightest tiles blend in with the seams (my edit isn't doing a good job at fixing that though, I don't know what colour would be appropriate).

I'd also suggest using something other than blue for the bulk of the background. Now the background and the character have similar colours. The pink one didn't look much like a bathroom, but it did make the characters stand out.

You can ignore the alternative shading if you wish. I feel that the dark part ends too abruptly.
The important edits are:

-I changed the shading om the uppermost stones. Unless you've changed them to be rounded they're out of perspective.

-The posts are too long; they look like they end somewhere between the middle and the front of the well.

The two biggest problem I found:

-Different pieces of armour are difficult to tell apart.
-Parts don't line up correctly. In the image I used the knees as a measuring point.

I've mostly done some colour changes. I mostly just dislike neutral greys (maybe a bit too much).

Otherwise, I (half accidentally) turned your ticks into small bars. In my opinion the ticks in your version contrast too much with the bar they're in, but you can probably also solve this by decreasing the highlight as Eischiya said.
I agree with Eishiya about the green bar and the dark brown. You also have a dark green that is so similar to the dark blue that I didn't notice it until I almost finished my edit. I don't think that is necessary either.