I know you didn’t ask about this but I’d add texture to either the wall behind your bed or behind the dresser. I agree maybe get bedding and pictures then decide colors?

I wouldnt add any accent wall. The room isnt huge and keeping all one color makes it look a bit larger. I would add some bedding with some brighter colors in there. I dont see a lot of lighting, so maybe move the two lamps you have, one to each corner of the dresser, and buy newer taller ones for the night stands, that go with the ones you already have. The windows could use some full length draperies, even if you want them sheer. Maybe wait until you pick bedding, and add the draperies in one of the colors in your bedding.

Lavender and gray look great together:

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Painting the walls all one color (other than gray) would look good if you get bedding with some color or pattern, but here's an example where someone paneled the wall behind the headboard and painted it a dark color.

Homey Project · More Info

I happen to love gray bedrooms but IMO a nice classic look not dorm room bedding slapped on a bed. This is one of my faves and so elegant and no color need. We need to know a bit more about you and your style to answer this .We do not even know if you are male or female that has a huge effect on decor. Accent walls are not plopped in a space to add color they need connection to things in the space .

Warm up the room with some pattern as well as color. Wood roman blinds at the window as well as lamps with warm rattan shades would introduce texture and warm natural color. Note all the wood touches in this gray bedroom: nightstands, floor, bamboo shades.

This Wayfair link is to lamps with rattan shades or bases--very pretty and will cast a soft glow.

https://www.wayfair.com/keyword.php?keyword=bamboo+lamps

Bedrooms by Mary Hannah Interiors · More Info

A horizontal skyscape, landscape, or still live above the bed would create a dreamy mood and introduce a bit of color that you could repeat in a throw on a neutral bedcover and colored pillows--golds, greens, reddish tones with just a bit of gray.

38" x 26" Seasons End Gold by Avery Tillmon - Print on Canvas Fabric Multi-Color · More Info

Bonita Painting · More Info

Abstract Landscape Acrylic Painting on Canvas, 24x24 Greens, Creams · More Info

"Floating On Air" Original Artwork By Preethi Mathialagan · More Info

I wouldn't paint an accent wall but you can do some board and batten on one wall painted the same colour as the other walls. Add some texture and layers: accent pillows, throw, area rug, window treatment.