Picture Editing Program Needed

I need help!  I have been working to find a new picture management program, as I am no longer able to use the one I had for so many years.  It was JASC--very simple to resize, crop and adjust color without having to understand how to do layers, etc.  Does anyone know of one that will allow me to add a square black background around my painting image without a lot of trouble?  That is a requirement now for entering artwork in online competitions, especially CaFE.


Here is another preview for my Open Studio Event:

This one is 7"x5" oil on board, entitled "At the Art Show."  I snapped the reference for the painting at an art show in El Paso some years ago.  I was intrigued by the image of a dancer standing in front of a painting of a dancer.  The "painting" on the right is one that I made up to fit this composition.  I had fun!


Thanks for your comments and input.