Q: customize Annotations

You can't.

There is no way to rewrite the GUI on the part of an end user.  Unless you're a die hard programmer and know FCPsvr's code really well, it's not going to happen.

I think Morad was asking because it is ostensibly a screenshot of Final Cut Server.

But it is a screenshot of the shot selection tool from an alpha version of Final Cut Server... since that feature never made it into the shipping product you won't be able to have an annotation window that looks like that.

Nope, that's a Photoshoped image.  Either way, the answer is no, you can't make it look like that, period.

If by "Photoshopped" you mean it's totally illegitimate, it's not exactly -- that was how the shot selection window was in an early 2007 alpha version of Final Cut Server, as seen in officially released Apple screenshots and videos... but it was the Windows version that was the original source of the screenshot.