AI Thumbnail Creator Setup

I'm looking for assistance in finding an AI tool to create vibrant and engaging thumbnails similar to those used by these YouTube channels:
- https://www.youtube.com/@TobsManhwa/videos
- https://www.youtube.com/@MamoruManhwa/videos

Requirements:
- Thumbnails should be colorful and vibrant.
- Important elements include:
- Text overlays
- Character images
- Background scenes
- Text style for overlays should be bold and large.

Ideal Skills and Experience:
- Experience with AI tools for graphic design
- Familiarity with YouTube thumbnail trends
- Strong eye for vibrant color schemes and layouts