Considering to watermark any texture-based mods I make going forward after finding someone uploaded one of my mods onto Steam Workshop without my permission. Already reported said mod on Steam this morning.
If I did, I wouldn't make visible enough for the end user to ruin their experience using it. More or less, it'd only be for my benefit if I couldn't tell if it was a re-upload or not. In this case, I had to pull up the textures side by side to tell.