I found some options from Lowes in your price range that would look good with your materials and have enough contrast not to look too beige. You can order them online and pick them up at your local store for no charge. Big box stores can be great places to find a good tile value. And I love that you can buy 3 or 4 sheets of tile, bring them home to see if they look good, and return them if they don't. Here's your space. Tile options start below. My favorite is the lantern tile. The hexagonal tiles are a very sexy look, but I'm not sure you have enough height in your bs. The glass and stone mosaic is a subtle look, but it has a nice level of contrast. The marble mosaic might look a little busy, but the colors are good. I hope these are helpful.

You are going to get people's individual tastes and ideas, which might not be what you like. I went through hours of photos and narrowed it down to half a dozen looks that caught my eye. I then searched for the manufacturer of those tiles and which local tile stores carried them. I went to see them in person and ruled out a few of them right away, as the photos made them look warmer than they were in real life. As soon as my kitchen is at the same stage as yours, I will go and borrow the tile sample boards from 3 different tile stores. Look at them in my space and make a decision. Your question is very open ended, so you are just going to get a wide range of tastes and ideas. Maybe if you had some sample tiles in your kitchen people can be a bit more specific in their feedback.

Do you plan on removing the curtains? Are you adding any additional lighting? I ask because both of those changes would affect the final paint color choice in my opinion. Right now, the curtains seem to be filtering a bit too much and adding more yellow to what is already there. Painting the small area under the sink also white will give you more options on wall color. I take it you are tired of the yellow overall. In your small space, I think you can go bold (me, I love red against white) but all depends on the rest of your color scheme in the adjoining rooms. What do you like? Do you want a more neutral, calming feel or something that pops? You already have a small backsplash so I would not add another on top of that. It is simple enough and goes with your retro look in the kitchen. Just paint the area above the 4 inch backsplash the same as your final wall color. A few small colorful prints (under glass that can be cleaned) would also add some nice contrast on the backsplash area. For hardware you could go either black or silver. Get a rug that ties in with your wall color but is not solid (just a few hints of coordination). Once you give us some more information on your existing adjoining rooms and what you like, I think you will get more paint color suggestions.

You could paint them to blend more with the greys. It won't look rustic necessarily, unless you were to distress the paint. - Just found an article that could give you some ideas. [https://www.houzz.com/magazine/add-timeless-charm-with-tin-tiles-stsetivw-vs~73021004[(https://www.houzz.com/magazine/add-timeless-charm-with-tin-tiles-stsetivw-vs~73021004)