Solved How can I change the slim login screen background?

I was looking in the slim.conf file if I could change the login screen background, but I could not find it. Am I overlooking it, or is that arranged somewhere else?
You're probably looking for this:
# current theme, use comma separated list to specify a set to
# randomly choose from
current_theme       fbsd
It's somewhere close to the bottom of slim.conf.

In order to use the fbsd theme you need to install x11-themes/slim-themes.
Oh, now I understand. I have to rename the picture I want to use to "background.png" and put it in this folder:
One more question though. How/where can I change the panel.png position. I use 3 monitors and now the position of the panel is half on the left and half on the middle screen.
I suppose I can change the x/y coordinates of the panel.png in one or another configuration file? If so, which one?
It depends on the chosen theme. Look for /usr/local/share/slim/themes/*/slim.theme. That file defines how the theme should look. You probably have to play around with the input_panel_* settings. I'd try 25% or 75% for the X position.

input_font              Verdana:size=10:bold:dpi=96
input_fgcolor           #000000
input_panel_x           50%
input_panel_y           50%
input_name_x            52
input_name_y            214
input_pass_x            -1
input_pass_y            -1
That was stupid of me not to check for the x/y coordinates in the slim.theme file first. But thanks anyway.
It worked fine by setting the input_panel_x coordinate to 50%