Improve tiny test dataset

[jluethi]

I'm collecting some ideas for improvements here of our tiny test dataset https://zenodo.org/records/14617240:

1. Let's improve the description (e.g. include what was imaged)
2. Let's improve the omero parameters of the image
   a. Let's choose different colormaps for acquisition 19 & 20
   b. Let's set reasonable rescaling defaults: 100 to 1500