All you can really control is colors, add a few custom images and select between icon sets, but nothing having to do with sizing or positioning.

My next step was to examine the DOM and whip up a GreaseMonkey Script that shrunk it. Having some experience with it, I made use of a few jQuery features in the script.

Before:

Before

After:

After

Enjoy!

Direct Download

// ==UserScript==
// @name           Minimalize iGoogle Theme
// @namespace      http://www.edwards-research.com
// @description    Minimalize iGoogle Theme
// @author         by James Edwards
// @include        http://www.google.com/
// @include        http://www.google.com/ig
// @require        http://code.jquery.com/jquery-latest.min.js
// ==/UserScript==

// Written by James Edwards
//		Feel free to use this script in any way you like, commercial or otherwise.
//		Attribution is optional but encouraged.
//
// jQuery Integration from: Greasespot
//		http://wiki.greasespot.net/Code_snippets#Use_jQuery_in_a_GreaseMonkey_script
(function() {
	//<div id="nhdrwrap">
		$("div#nhdrwrap").css("padding","0px");
		$("div#nhdrwrap").css("margin","0px");
		$("div#nhdrwrap").css("height","100px");
	//<div id="nhdrwrapinner">
		$("div#nhdrwrapinner").css("background-image","none");
		$("div#nhdrwrapinner").css("height","100px");
		$("div#nhdrwrapinner").css("margin-top","-20px");
	//<div id="regular_logo">
		$("div#regular_logo").hide();
	//<p class="gseaopt">
		$("p.gseaopt").hide();
	//<div class="personalize_link">
		$("div.personalize_link").hide();
	//<div id="header_promo_wrapper">
		$("div.header_promo_wrapper").hide();
	//<div id="promo" class="sandbox_msg" style="margin-top:-20px;"
		$("div.sandbox_msg").hide();
	//<div class="gradient">
		$("div.gradient").hide();

}());