Would it be possible to buy 10 GPUs on the cheap and set them up as a cluster? I'd like to generate larger stable diffusion images for instance, but don't know if a cluster would support this.
If the goal is to increase the GPU vRAM (which I believe it is, given that's the constraint on image size), the answer is "not really" for consumer cards. You need NVLink bridges for pairs of PCIe cards (which they have, but then you'd only double the vRAM), or NVSwitch on the high end data center servers (DGX/HGX A100).
You could, but you'll need server grade parts and a few good electric circuits. Oh and it costs hundreds of dollars in electricity every month.