I use the Affecton template in a bit different way that it was designed to be used probably. I do not have as much content as it was designed to support. I have only a couple of pictures on the page and very little or no text. The result is that the white background is very irritating:
I want something darker than white but I don't know how to find a colour that goes well with the rest of my template.
I looked at colorschemedesigner.com but it does not let me start from the existing palette.
This is a question that really cant be answered since it is based on opinion of ones desire in a color palette. Furthermore, you only provide a sample area and we have no clue on your end intentions or the layout of the entire site. I would strongly advise searching for color inspiration from other sites or head over to Adobe Kuler or Colour Lovers and browse around till you find something you like. Both sites will allow you to take colors you have already selected and search for palettes our peers have made.
If you have Illustrator, the color guide tool can be helpful. Based on your selection in the dropdown it will present you with various palette options.
In addition to the color harmony options in the dropdown, you can change up the palette parameters in the panel's flyout menu. Experiment with the three options at the bottom to find what you're after.
For a background color, you'll probably want to play with the L in Lab mode or the S and B in HSB to keep it subtle.
http://www.colorhexa.com/ is also a great alternative in addition to the ones listed above.
Colorizr.js might be a good tool to play with the colors and see what suites your taste. When you use this tool the idea is to configure color pickers for different parts of your page and then adjust and fine-tune those colors.
