RVsitebuilder 5.4 does support RVsitebuilder icon in paper_lantern already.
Update RVsitebuilder to the latest version.

RVsitebuilder is 5.4 already, but the icon still missing?
Please try the following.
1. Upgrade cPanel and check again.
If this doesn’t help. Please do the number 2.

2. Check if in your  paper_lantern has other plugins that icon missing than RVsitebuilder or not.
2.1. If it’s only RVsitebuilder icon that missing. You can run the following command to register RVsitebuilder icon again.

/usr/local/cpanel/scripts/install_plugin /var/cpanel/rvglobalsoft/rvsitebuilder/panelmenus/cpanel/cpanelplugin/register_paper_lantern.tar.bz2 --theme=paper_lantern
*one long line command

2.2. If some other plugins icons missing. This will cause the RVsitebuilder icon missing also.
2.2.1. Try to update those plugins and check again.
If doesn’t work.
2.2.2. You need to unregister and register those plugins again.
After that run the following command to register RVsitebuilder icon again.

/usr/local/cpanel/scripts/install_plugin /var/cpanel/rvglobalsoft/rvsitebuilder/panelmenus/cpanel/cpanelplugin/register_paper_lantern.tar.bz2 --theme=paper_lantern
*one long line command