Did you know that you can change the widths of your gadgets on iGoogle? To do this, click the down arrow to the right of one of your tabs and then select “Edit this tab” from the drop down menu. You should now see this window:
This is making me think that I should add an option to the Tree Frog, Fish, Spider, etc. that lets the user set the height of the gadget. You could then fill one whole tab with one gadget or you could make some small square gadgets with the four column configuration.