if you want it at the bottom, all you should have to do is putt the image tags at the bottom of your script, inside the body tags of course. Hope this helps.
If you cut it up using photoshop it should use the same picture of the bg with i think is Earth, im not sure if you would want to use that but its an idea :)
for your background in the iframe, use the cut background picture instead and make the picture fixed so it doesnt move but you can still scroll. You can maybe use this:
<BODY Background="image directory here" bgproperties="fixed">
I think it is called visitor font (Visitor TT2 BRK). Here is a download that i set up for you: Visitor Font
Use 3pt font and the anti-aliasing to "none".
This is what it looks like:
Hope this helps.
Maybe you could have a drop shadow on the pictures to make them stand out more, im not sure how it would look but it might be worth a try. Also the lines above the navigation sticks out. Good job for a first website though