I wanted to add a custom icon for the OCS broswer tab.

Attached are a couple of files to choose from if you want to do similar.

As currently named favicon.ico is an observatory with stars and favicon_1_.ico is stars. Place the one you want in the root of your SD card and name it favicon.ico.

Then in OCS.ino add:

www.on("favicon.ico");

after:

www.on("index.htm",index);
 
The art work is not mine. I got it from this free site: https://thenounproject.com/term/observatory/1336/

(but I just did a screen capture vs. signing up for a free account to download)

Then manipulated in Photoshop (with a .ico filetype plugin)

Observatory favicon:


Cheers

Very nice icon.
Is it responsive on smartphone ?

I have an iPhone. It works in chrome. favicon shows in the tabs view. In safari you have turn "show icons in tabs" on in safari settings. Other's showed immediately but I think the lack of one on my page is cached and it will take a while to show. 

I'll try on my iPad... Yeah, it works.

Can't speak for Android, but since it's chrome, I would expect it to work.