So I have css code as follows:
.jumbobg {
background: url(\'http://znc.mane-frame.com/static/silverleaf.png\') fixed
The thing is that you have specified two backgrounds in background property (separated with comma), so you have to do the same with background-size to get their distinct values, when you specify only one value in background-size it is applied for both images, to be clear:
background-size: 50px 80px; - this is one value
background-size: 50px 80px, auto; - those are two values
Use comma separator as you did in background, so for example this should work as you want:
background-size: 50px 80px, auto;