Paint the walls, reupholster bed, or replace bed.

Find a beautiful bedspread or comforter to go with your headboard. Next find window treatments. Then go to the paint store with the comforter and curtains and pick a paint color. For under $100 you can buy a gallon of custom color paint, brushes, rollers, and drop cloths. Spend two days and repaint the room . It is a skill that will serve you well the rest of your life, saving you thousands of dollars over having a pro. After this is done, you can take your time finding accessories like lamps, a little chair for shoe-putting-on, a small framed mirror, and some pictures for the wall. I shop at consignment shops for expensive furniture at one third the original price. For instance, I bought an Ethan Allen upholstered chair for $400, not $1200 which was the original price. But, please, don’t paint first then try to find bedding. Paint is the last thing to choose because it comes in nearly unlimited colors while fabrics do not.

I agree with adding curtains and pictures on the walls. Paint is one of the most inexpensive items in decor. Gray is a cool color and beige is a warm color. That's probably why your room doesn't look right. Changing the walls to a warm color may work well. Cool colors: bright white, ice cool pastels, black, gray, royal blue, purple, bright yellow, pine green, Kelly green, forest green. Warm colors: off-white, sand, beige, tan, brown, olive green, peach, orange, golden yellow. Painting your walls a warm light olive green may work well. https://www.sherwin-williams.com/homeowners/color/find-and-explore-colors/paint-colors-by-family/SW9037-baby-bok-choy In my opinion, buying upholstered furniture at a second hand shop may not be the best idea - they may have bugs in them. Wood furniture is ok to buy there, because it can be cleaned. If there are bugs in upholstered furniture, you may not be able to see it and it may be impossible to get cleaned.

I agree with previous posters to find some bedding/coverlet that you love. The current gray comforter is fighting your upholstery. Is it possible to center the bed on that wall?

IMO start with some really nice bedding and get the bed centered on the wall with night tables and lamps on both sides and more than that will require you to post more pics and a to scale floor plan. I love drapes in a bedroom and honestly guest rooms should not look like you dumped all the stuff you didn’t want in there. Once you have the bedding then choose a color from it for the walls and drapes. I love paisley bedding it is gender neutral and has nice colors to work with. This is a good example to work with the bedd and the carpet and then do the walls and drapes in a pale teal

I found some bedding that I both love, and I think it might coordinate both the walls and upholstery. I tried to center the bed a bit more but that can be done even more once I get night stand(s) or a better side table (black hand me down will GO). I’ve always heard you should put the headboard of bed opposite the door so it’s what you see when you walk in. But should I just line it along the same wall though so the upholstery isn’t so obvious? I’m spending big bucks on my open living/dining space on the main floor (so excited to seek ideas and help on that once my custom sectional and credenza arrive!)...so this really needs to be a low budget room.

That bedding looks quite nice. I think the room just needs some character now. Maybe a small rug by the side of the bed, in some pretty tones from the bedding etc and some items on the wall and a lamp on the side table. I think it is the starkness that is making things stand out as much as they do right now. A few nice prints on the wall, maybe a faux plant for some greenery. If it is a guest room and you have space, a small chair is nice, or a least a place where a guest can put down their bag. Maybe a small bench. Also a mirror is a nice touch, even if it is just a small wall mirror and I'd put it above the dresser. And some nice curtains to cover that blind, or a nicer blind. Maybe a woven rattan roman blind would be nicer.

I‘d try bed on opposite wall and see how it feels. Simply layering the bed will make a huge difference and can’t beat using white

Try Marketplace for nightstands; it’s amazing what can be found. Add some pictures, a chair would be handy + a mirror over dresser - again second hand and check IKEA for their white or grey/white stripped Roman blind for $30 or rattan

If this is an infrequently used space, then changing the wall color and adding simply white curtain panels will be a nice base that you can add more touches too later.

I agree center the bed in the middle of either wall. You don’t want your guest to have to crawl over one another to get off the bed. Find a colored bed dressing , maybe even a little busy and curtains to match as d tt it he rest will fall into play