Ah yes, well there are different varieties of cholla, and the ones I've seen have the more typical "cactusy" look, with single spines fairly spaced out.
Oh I am familiar with creating 3d effects with Inkscape. It may be that I'm not experienced enough to find it easy. I can do it, it's just that yours is so polished and perfect looking. I'm sure all I need is more practice

I don't know that you have to create something different, or much different than what you've got. "Swampbot" seems to be a fairly mythical or cartoony kind of character, and I don't see why "swamp cactus" wouldn't work, lol. I guess it depends on how fanciful you want the image to be, in the end. I mean, I can see something like algae, slimy stuff hanging, running and dripping off your swamp cactus. Maybe it even oozes out of it? Yeah, don't mind me, I think my mind is permanently stuck in brainstorm mode, lol!