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.

What was the outcome. We are currently having a pool repair and have the same problem. I feel they are using the wrong coping size. The men doing the tile work said it was the wrong size but the pool company told them to put it in anyway. They want to send someone tomorrow to caulk.

I've never seen an installation detail showing the wall panel overlapping the flange. That would require shimming the panel after the base in in place and if the wall panel gets too close to the shower base water can be drawn up into the panel. In your case the mistake was cutting the wall panel so high above the pan flange creating the grouting problem bry mentioned. You might be able to use a Z flashing or larger tiles (see below). You could cut 1/2 or 3/8 x 12x 12 marble tiles in half and place them horizontally in a running bond pattern solving the bottom edge issue (see below). You could add a narrow 1/2" thick strip of wood at the bottom of the wall board to reduce the gap and install a Kerdi membrane over the entire wall. Its difficult to tell from your photo how close the shower base flange is to the studs but assuming it is no farther than 1/8" from them here is the standard tub and shower base detail for tile or solid surface panels: For an excessive gap a Z type flashing might be appropriate: Be aware that a silicone sealant joint should be deeper than it is tall so it forms an hour glass shape in section allowing the silicone to stretch without losing adhesion. This is easier to achieve with 1/2" or 3/8" thick marble tile than with eased edge ceramic tile.

millworkman, I will ask them about this, thank you for your thoughts! We are in South Florida, so right now lots of heavy rain in bursts. We got about 8 quotes and not one recommended busting out old tile. They said there is metal and concrete by the sliding door so they chipped out what they could, we did tell them we are replacing doors in next year. Also we have a covered area that has composite decking and now the pavers, while not level to decking, are much closer in height than before, maybe that's why no one recommended demo of old deck?