The process of making these thumbnails was very interesting. First, I was provided a screenshot to use as a background. Next, I was told what characters to use and a vague idea of how to pose them. Everything else was left up to me.
A criticism I have with Minecraft thumbnails is the characters don't look like they are a part of the scene and completely lack any lighting or shading. For these thumbnails, I reconstructed the lighting from the screenshots in the 3D scene, sometimes partially reconstructing and modeling parts of the screenshots for accurate lighting.
Adobe Photoshop was essential in my thumbnail-making and was something I used constantly. Besides adding the logo and border, I used it for color correction, adding bloom, film grain, chromatic aberration, DOF, and motion blur, as well as shadows and extra lighting.
Some thumbnails used 3D environments rather than screenshots. For Episodes 7 & 14, I used a 3D environment because of how the characters were posed in the scene. I found this way much more convenient than having to composite the renders into the backgrounds and shade them, and decided for the next season to use 3D environments instead.
Starting with Episode 24, the series creator asked me if he could help with making the thumbnails. I agreed and sent him an incomplete version of episode 24's thumbnail. When he sent it back, I adjusted it and corrected the lighting to keep it consistent. For Episode 26, he made it completely himself. I didn't have the time to make a lot of adjustments, but eventually, I did give it the remake it needed.
This was one of the first fully rendered animations I ever made, with work on it starting around November 2023.