I would like to ask whether you sort images after approval to categories or leave them as they are?
Do you think it helps to sell and it is worth extra time spent on it?
Thanks for your opinions.

No

I would say yes (unless you are one of the big uploaders who drop 200-300 on a site in one go at a time). I sometimes forget to do the category thing and can actually notice the difference in views between those and similar images not loaded long before them. It actually pics up after I categorize. The site makes active use of its categories and it all depends if buyers make use of it. In my experience they do.

Worth your trouble? Update a few batches and check.

PS: Canstock is one of my best selling sites, but I also must add I make use of the public galleries and place pictures into series (do not know exactly what part categories plays in the sales, but sometimes what you are prepared to put in, is also what you are going to get out).