I'd go with the Corsican mint......creeping thymes would really prefer to be in full sun and a northern siting with minimal winter sunlight is not going to be their cup of tea :-) Ask at your local nursery/garden center for the availability of growers flats. These are solid (no pots) flats of groundcovers that are typically used by landscapers, although helpful for homeowners with large areas to cover. They tend to be about 1/2 the cost of potted plants. With low, mat-like, root-as-they-go groundcovers, you can just separate appropriately sized plugs and plant in between the pavers. Each plug will have enough roots for the plants to 'take'. And you can space the plugs to fill in according to the spacing of the flags and your needs, not by some prescribed spacing that may not apply to your situation. Groundcover seeds are not easy to find but that would be an equally inexpensive approach although much slower.

I wish I had thought of that when I bought my new runner at Christmas. My table is 10' long and the runner looks skimpy on it. Bet I cannot find another like it now. :( My runner is goldish in color (in the same family as my dining room side chairs - although they look tan in this photo.) I realize (after seeing your post) that it does not match my host/hostess chairs. They have a grayish/tan tone, and no gold. Oh well! I also could not find a rug large enough without having to pay a fortune, so we just have to make do.

I love the paint job and the bed is gorgeous, but it seems like the two don’t work together and that’s what’s throwing it off for me. If you were to put that same bed, bedding and runner in a room that’s painted a soft creamy tone of white or off white, it would look amazing. ETA: And I think the quilting adds character to it. Once it’s used for a bit it won’t have the stiffness it does now, it just needs time and maybe a little use. Also ETA: If you’re not a fan of white, you could always use a different color, I think it’s the stripes that are throwing it off. (And with all the taping to make them I can only imagine how hard those probably were to do, so I’m sorry to say it)

your wood actually looks like doug fir. I don't know if they were meant to be covered. you can tell by the way they were installed and finished if they were meant to be stained. I'm guessing since they are raw, they weren't. It's paint grade wood. if you stain them, it will prob look like this you can always paint the risers and get oak treads and stain those. Or just give all the wood a very good sanding. clean up all the rough spots and sand smooth. use a vac to suck up every spec of dust and wipe w/a damp rag. now prime them. do a fine sand when dry because the primer will give the wood 'nubs'. you want those nice and smooth before painting. clean up very well and get every speck before you start painting. use this primer paint. Advance is beautiful on wood. you can also use Zinsser oil based primer. If you want to try staining, use a dark walnut (general finishes) Gel stain. then top w/general finishes