> At the time this was Stable Diffusion on the backend

The community made models (merges, fine tunes, etc) of that era are all completely overtrained and optimized for portraits and frontal shots. They would try to make a person out of anything. Inpainting faces is already a chore, even with a lot of tooling around that, but inpainting anything else is almost impossible. These models are also especially bad to fit objects naturally into scenes. You can make a crappy necklace or belt work, but introducing a new object into a scene just fails with infinite variety.

They are also much better using 512x512 as resolution, any larger deviation introduces more problems.

Considering you wanted to inpaint banner ads, they would probably get distorted heavily. Those models can't deal with fonts and are bad at a pixel perfect transfers. The only viable way to do this, at that time, would be to manually insert the banner ads and fix the seams with AI. Requires some artistic skill of course.

Your attempt was bold, but with the expectation of just supplying two images and let the models do it, it was impossible.