Attempting to create a mod Lichess theme -need help-

The original Lichess theme for stylish named "Zurich Lichess" can be found here: userstyles.org/styles/102576/zurich-lichess
Code I'm trying to modify is this: http://pastebin.com/guyQeEbN

Here are some previews: http://prntscr.com/55332b | http://prntscr.com/5533jv

Basically what I'm trying to achieve is so this theme doesn't replace all of the other chess sets but rather add it to the top right options.
Example: http://prntscr.com/5539xm

I'm quite novice with CSS, help appreciated.

Complete removal of the yellow board and reverting it to the old default board board would be best. I think it would save some time in creating this mod because it currently goes unused by me(original theme creator added it).

This is the final CSS theme I'm aiming for: http://prntscr.com/553jzl

Sorry for being such a perfectionist but I'm a graphic designer :p

The theme "Zurich Lichess" also conflicts with the 3d chess piece themes. If a fix for repairing 3d theme's is easy then by all means include it in this stylish mod.

I've been told this impossible via CSS and only through something like tampermonkey using a script.

Where'd you get those piece images from? If they're open source, or otherwise free for us to use, we'll likely include them natively in lichess.

The piece comes from chess24. We can't use their material.

Yeah they're from Chess24 I believe... You don't want to get into trouble.