Thank you ALL so much for commenting and sharing your wisdom and experience.
Today, I started the work with photographing my wardrobe. I decided I will do it by category and start mainly with Fall/Winter items.
Thank you for the advice with the online stock pictures, I managed to find some. Most of my old and thrifted items will have to get photographed though.
I managed to photograph almost all my F/W blazers, jackets and outerwear. It went relatively quickly, although the pictures are not very nice. I will maybe change some of them later, but for now I would like to get everything into a digital wardrobe to be able to create Custom Finds and use Stylebook.
I also took pictures of some of my bags - it was easier than the clothes.
I used hangers, as recommended. The most difficult part was the hanger appeal - have not succeeded with that. The colors, on the other hand, were rather correctly shown in the pictures.
My overall impression at the moment is that it is less time consuming than I imagined, I thought it would be almost impossible to get it done. It takes time, yes, but if done in smaller portions, it will be manageable. I look really forward to having everything organized and improve my shopping and outfit planning, and simply have a better functioning wardrobe. And - it is quite satisfying and fun.
Thank you again for the encouragement!