As the appearance of the garden has a modernist style with the straight lines and concrete furniture how about a Mondrian influence and add a bold strip of blue? It is a pond and with the right shade it could look really relaxed and contemporary. My daughter's suggestion is a chalky lilac!

All the suggestions above are perfectly good. However, when you have a house that is entirely painted, the options are so endless that it's easy to get stuck. I'd advise either finding photos of comparable homes in colors that you really love, and reproducing a similar palette on your home… or upload a picture of your house to a colorizing site, and play around with various combos. Sherwin Williams has a Color Visualizer that is decent. I don't mind a white house, but feel that the black trim is a bit harsh. On the railing especially- it feels like it is outlining itself too much. Reduce the contrast between the body and the rail and it will enhance the house rather than overwhelm it. You have a lot of choices, so just experiment and go with what resonates with you.

Teal? Just a thought sometimes I think it's smart to match or atleast go with the curtains you'd see in the window

Oops! Your trim looks grayish blue to me. Sorry, didn't see it is charcoal until afterwards...well in that case, I think I would still do gable and wrought iron as mentioned but then try a bright yellow, like SW's BEESWAX is paint color. Are you in the islands? Sorta has "that look". Envy : )