The rule of thumb with mirror size is to leave a 2-3" gap between the backsplash, sconces, lighting fixtures, etc. from each side of the mirror. As long as the space is the same on the 3 or 4 sides, it'll look like its made there. We do custom mirrors and would be happy to send you some free samples to take a look at! www.framemymirror.com and you can also email madison@framemymirror.com for design help, sizing help, and pricing :)

A few comments - part your issue might be the pictures you're hanging or the height at which you are hanging them. The average human eye is about 55" above the floor - which make that height ideal for centering pictures and mirrors. With the wainscot, you might have to deviate from that and use the window as a guide. The size of the picture over the toilet in relation to the mirror isn't working. You may want to consider raising the light fixture if you keep the current mirror so could be hung a little higher - but I would opt for raising the light fixture and use a different mirror - whatever style you like best. Also, with the right tools you could use picture frame molding to frame a plate glass mirror and mount the fixture through the glass - this could give you a larger mirror and bit more flexibility with the pictures you hang adjacent to it.

Go online. Check Thibault. They make beautiful damask wallpapers, if that is the direction that you want to go. There are lots of websites that will allow you to get samples. And that sell high end papers for less, if budget is an issue. Why not change things up a bit? You have a beautiful powder room. No need to change anything. Just wallpaper. Why not be bold?

Hello- in our new home and need mirror help for the powder room. Pic of vanity, 55in. 9ft ceiling. Black hardware all downstairs, as well as window in this room.