Burd only offers a small amount of themes that come pre-installed. Currently Burd IRC themes are designed with css.
The public is free fo make themes for Burd IRC. There is a github repo that you can request for your theme to be added to if you wish.
The default theme is a simple grey theme.
A theme that uses different shades of purple throughout Burd.
A theme that uses different shades of blue throughout Burd.