Reflections in Paintings

I have been creating paintings for personal use, rather than uploading them. So far I have created about a dozen sets and have also created murals to look like very large paintings. My question is this, I want to make it so my painting/mural has a reflection (no a mirror effect, just a faint reflection), like there is glass inside, unfortunately I don't know how to do this, can someone point me in the right direction?

Thanks
deejay21