1) Movie player which can export the current movie position as a still frame, e.g. LosslessCut
- Goes really quick.
- Automatically creates images in folder near your movie.mp4 by the name scheme <moviename>-HH.MM.SS.mmm.png so they are in chronological order and you get all this with zero additional work.
2) An image editor which can create an image collage from multiple image sources, e.g. GraphicConverter and its Collage function
- Create new collage
- Make sure it has image placeholders for as many images you need
- Set your grid, e.g. regular 3x3
- Add files from Finder or GC's browser into the collage file list or directly onto a placeholder on the canvas
- Drag files from file list to positions on canvas
- Save collage