I recently contacted Coderwall support about me not being able to upload a new background image on my account. While the issue was resolved quickly, I also tried to craft the perfectly visible background image for coderwall. I did ask coderwall about the perfect image size, and Mike (@just3ws) replied to me with a size of 760x333 pixels based on the profile div dimensions. However, I soon realized that this was not enough, as coderwall css resizes the image to 840px wide:
So, I took on the task of perfecting the pixels in Inkscape to create a template image for coderwall. I fired up my Inkscape (after realizing that Pinta can't give me the pixel perfection I was looking for). So, without any further delay, here's the template image that you've been looking for:
You can download the original svg/png from my Github repository.
This is how the image appears if used as background image (blur removed for clarity):
Color Guide: White is invisible region, yellow is the visible background, and blue is your avatar image.