As someone who regularly does image modifications, I always tell people that they should
ALWAYS sign their art, and not just in one corner - if possible,
work your signature into the art itself somewhere close to the main focus of the image so that simply cropping a pic can't be used to remove it.
Given the complexity of your work, it should be easy to work your signature unobtrusively into the background patterning (for example, in the scrollwork on the decanter or the deck of illusions) near the center of whatever you happen to be illustrating...
As an aside,
always put the "

Date YourName" text on the pics. (In some places, simply placing the copyright text on a pic is enough to establish copyright.) If you ever want a website to take down one of your images that someone posted without your permission, you're going to need to be able to produce the original image with the copyright text on it to even
begin to prove that it's yours.