a few BM colors Silver Cloud, Polar Sky, Misty Blue, or Rivera Azure (matches tile)

Based on your post it sounds like you may want something other than light blue or grey. If so I think you could do any number of colors on the wall if you pull a little more blue into the accessories so the blue becomes an accent rather than the focus.

Maybe a soft yellow or turquoise with bright accents:

[Traditional Bathroom[(https://www.houzz.com/photos/traditional-bathroom-ideas-phbr1-bp~t_712~s_2107) by Dallas Interior Designers & Decorators Dona Rosene Interiors

or a more formal look with taupe wallpaper and floral accessories:

[Traditional Bathroom[(https://www.houzz.com/photos/traditional-bathroom-ideas-phbr1-bp~t_712~s_2107) by San Francisco Interior Designers & Decorators ADEENI DESIGN GROUP

What would your ideal be if you didn't have the tile as a limitation? is there a way to tie the tile into your dream?

I'd say find some accessories that have that blue as part of the color scheme. Then pull another color from them for the walls. Like above, but in whatever style you like.

Light blue and Light grey are fine (although I have several other greys in the house & it seems odd to bring in yet another) --I just didn't know which light blue or grey.
:D

I think you have a lot of options with that beautiful tile! What style do you want? For dramatic, I'd be tempted to go a deep dark rich blue (almost navy). You could go gray (any shade from light to dark) and really just about any blue. A light but sunny yellow color could work really well too.