The forum software allows CSS, so we can do all of those. Since we have a full fluid layout as well as a max-width one, both of them flexible, I suppose we could use fade outs to a solid background color or repeatable backgrounds as you said. If there's an important part at the right side like the snowman, we could in theory also split the header image. Or use different widths at certain breakpoints.Dimensions
Keep in mind, if we make a longer image, it will stretch or not fill the entire 100px height in that case, so you'll either be left with an ugly stretching image, or something that's shrunk down in height to fit the width. Remember that images are static sizes. Ideally, if the forum software allows, you could do a few things:
Again, I'm not familiar with this forum software. I'm a skilled web designer + developer of 17 years — so I'm taking educated guesses here.
- Center an image and apply a similar background color behind it
- Make a background image fill the entire block, and overlay a second image for the logo so it sits within the site's frame.
- Provide multiple widths for the image and have the forum choose which one, based on the site's theme selected (e.g. fluid vs. fixed)
So yeah, basically it would have to look good for all window sizes. The only constant is the left side logo position: The logo + text is a clickable image.
Minimum width is 691px. Below that the header image isn't shown.