Here are my resources that I've made which you can freely use on your site.

Buttons

(^^^This one was actually made by my friend Nim at haunt-fm)

Graphics

Stardust Speedway Border Image

This is a CSS border image that can be used to make dynamic borders for divs in the style of the Stardust Speedway level from Sonic CD. The original assets are by SEGA, and I cobbled together this image from the tileset here: https://www.spriters-resource.com/sega_cd/sonicthehedgehogcd/asset/140582/.

To make this display correctly, you need the following CSS on the class you want to display the border with:

border-image-slice: 64 32 64 48;
border-image-width: 64px 32px 64px 48px;
border-image-outset: 64px 32px 64px 48px;
border-image-repeat: repeat repeat;
border-style: solid;
border-image-source: url("PATH_TO_IMAGE_HERE");
background-color: #010024e0;
margin: 64px 32px 64px 48px;
padding: 16px;
					

Gold Plaque Border Image

I made this in Blender. If you'd like one with different lighting or colors, I may be able to help if you email me.

Dithered version from Dithermark:

Border image CSS:

border-image-slice: 19% 19% 19% 19% fill;
border-image-width: 64px 64px 64px 64px;
border-image-outset: 0px 0px 0px 0px;
border-image-repeat: stretch stretch;