Here are the steps if you need them......
Have your pictures on your C Drive. Pick you picture, resize it to the size you have your ReefChat background set for (I use 380 x 120) and then save it as a .PNG format instead of a .JPG.
Go to Edit on your ReefChat Geg Gen scroll down to Background Image, hit Browse.. Go to the location on your C drive where your .PNG picture is and select it.
It will become your Sig Gen Background. Now save it at the bottom of your Sig Gen. As stated it can take several minutes to see the file make the changes.
If you ever want to change pictures, you first have to delete your existing picture in the Sig Gen edit, your background should go back to blue, then you can change pictures.
Hope this makes since if it’s what you need. Good luck!