My suggestion to tie in all your beige fixtures with gray is to take special note of the base note colors of the gray paints you use. On the color swatches for whichever paint company you choose take notice of the darkest color on the swatch and whether it has a brown, black, green etc. tone to it. I would stick with a taupe colored gray that has a warm brown base note. Then use a pattern in shower curtain that has beige, gray and taupe to make it all look deliberate. Towels can then pull out any of the colors in your pattern. Here is one example as a stepping off point.

Thank you! I will follow your advice regarding the base tone, excellent tips.