If anyone wants to experiment with theming their web gui you can create a custom file that will override the default file by copy the contents of omv.css to omv-custom.css:
cd /var/www/openmediavault/css
cp omv.css omv-custom.css
This will copy all the contents from the default css file. Any changes you make to the omv-custom.css file will override the default. You will see lots of items in custom file you created that have hexadecimal numbers for colors. You can use one of the following sites to choose new colors and then experiment.
http://www.colorschemer.com/online.html
http://www.colorpicker.com/
The sections that you will probably be most concerned with are the login page section and the workspace section. The login section is the sign in page and you might want to change your background picture. This is the section you would want to change to do this:
body#login-page {
background: url("/images/test.jpg")no-repeat center center fixed;
background-size: cover;
}
The body#login-page is not in this format now so you need to make changes to it like the code box.
Then you will need to change the name of the test.jpg to then name of you jpg file. You jpg file needs to be put in this location:
/var/www/openmediavault/images
The chown of the jpg file needs to be openmediavault:openmediavault
and the chmod need to be 664
so you would do it like this assuming your test.jpg is in the /var/www/openmediavault/images location.
chown openmediavault:openmediavault test.jpg
chmod 664 test.jpg
Do not be worrried about messing up the omv-custom.jpg file. If you do you can just delete it and the defaults will be back and you can copy the default file and create the omv-custom.css file again.