It took me a while, but OGS now supports custom board background! (I am still keeping custom stones and “blind/one-color” versions in mind, will add that later hopefully)
To add your own background:
- Click your upper right avatar.
- Select “custom” board option, and 3 new elements will appear.
- Paste an external link to your desired image. This setting will be saved locally and is device specific.
The link provided needs to be a direct image link (with no other elements on the page, just the image)
The simplest way to achieve this is to right-click any image you are viewing (or uploaded to some image hosting website) and selecting “copy image address” or “copy image link” (or something similar depending on your browser). Now just paste (ctrl+v) into the OGS form, all boards should immediately update with the selected image.
Pretty much any format is supported, the images can be transparent or vector or animated gif as well and do not need to be square, but in that case part of the image that stretches over the goban will be cut-off.
If you have some unique pick, you can brag here