I think if the walls "come out" more towards their bottom (think Zelda perspective), I think they'll read better. Think of the stingrays as your vanishing point, and design the wall tiles so that they appear to "point" towards the stringrays most of the time. Obviously with tiles and moving on the screen they won't always be doing that, but that's a good place to start. The walls just pointing towards the bottom of the screen does feel a bit weird with the perspective on the characters.
I think the tilt on them will be noticeable if it's part of an animation reacting to the player's movement. It's barely noticeable when displayed side-by-side like that, but these things tend to stand out more when being swapped out on the same character.