Would be nice to can search by image any picture when you Right-Click on it and Select "Search by Image" to open a sidebar with the image matches the actual picture you looked for. This improvement would save seconds for many users who "Copy the image link" or "Save Image As" and then go on Google for Reverse Image Search.
I'm sure many firefox users with no Image Search extensions are looking for this feature for long.
P.S. If the post get many upvotes (Kudos), then Mozilla Staff would take in count for the future versions, considering many users want this feature on Firefox.