As Larry says, Adobe imaging software does have round select tools. They are not as easy to use as rectangles, but they are there and I use them from time to time. You also have the option of an ellipse, which is nice for portraits.

My comment was mainly on the time required to do such a picture as you show. A scan of the objects themselves on the glass is very quick, but won't have the artistic style of a collage such as you created, but is fine to show lots at auction.

You mention hard to scan items... I find ashtrays come out better scanned than photographed. You might think that 3D items would not be rendered well by a 'flat bed' scanner, but they are. I've even found that I can remove the reflection that sometimes shows up on a glass ashtray by cutting out the half without the reflection, rotating it and overlaying the other half. This only works for symmetrical designs, of course.