There seems to be a mismatched of scales on the elevation. The center section is of a larger scale with high eave and a wide tall door and the side parts have low eaves and low window heads possibly no taller than 6-8 AFF. Lowering the window heads is a big mistake because it greatly reduces the natural light in the house and lowers the apparent scale of the house making the center section and door look out of place. IMO windows should be taller than exterior doors unless a transom is added above the doors. The lowest-common-denominator height alignment approach is the result of the post war building boom. Today there is no reason to use short doors and low window heads if the ceilings are taller than 8-0. A "standard door" size is effectively whatever distributors or retail vendors keep in stock. I usually use TruStile doors from Colorado because they are made to order. Interior and exterior doors heights are 4 ft to 12 ft in 1/16" inch increments. Doors over 10 ft tall are not covered under warranty. Shorter doors are made in smaller widths.

In our last house the powder room had about the same sqare feet as yours does, just different dimensions. We had three halogen lights above the mirror and that was plenty of light for everyday use. I don't remember the actual bulb we used as we haven't lived there for almost a year. Just look for sconces that allow a brighter bulb or that use two bulbs in each sconce. I would use the lumen formula davidtay posted above. That will help you decide if the sconces you like will be bright enough. We did have a bathroom fan with a light installed above the toilet. That helped for when I wanted to clean the bathroom, or needed a brighter light for removing slivers, etc. as the bathroom was where we kept our first aid kit, but we could have gotten along fine without it as the light from the vanity fixture was enough for the room.

I have a 3.5' by 5' powder room literally tucked under the stairs. The door is only 20" wide. I seriously doubt that it meets code but it was here before we bought the house. The previous owners' son was a plumbing contractor. It does function as what we call the "world's tiniest half bath". We remodeled it a couple of years ago. The hardest part was finding a sink that would work. The best part was choosing tile for the floor. With less than 18 square feet of flooring, even the most expensive tile we liked didn't blow the budget.

On another trip to Home Depot, The HD guy was kind enough to "carefully" situate eight 60# bags of Quickcrete cement (480# total) throughout the car! I used the same Toyota method of calculating five adults (approximately five 100# Japanese people -- maybe realistically 1 adult and 4 kids equating about 500#?) I figured I was safe for the 1-mile trek home. I shoved the Quickcrete out the door and it's still sitting in a lump -- thank God for gravity! I can't imagine that much laminate flooring in a Prius but given CBS 60 Minutes' recent expose on Lumber Liquidators China supplier problem of mislabeling its laminate flooring as CARB2 compliant when it clearly wasn't, I'll believe anything. I'm ready to rip out my LL flooring in favor of real wood or tile... That shall be my next project after I finish my garden beds and my new money tree starts to bear fruit...