Ok first for - "I think I got it."
You can add to the css file as many NAV sections as you need. (nav, nav2, nav3, etc)
You could even call them something else, like...
navindex, navabout, navcontact, etc., you keep all the code the same for each but change the the name (navindex, navabout, navcontact, etc) and change the picture (pic_index.jpg, pic_about.jpg, pic_contact.jpg, etc)
Now the code in the index page (the index.html) would be
<div id="navindex">
The code would refference the css file to file navindex and would display that picture.
if on the about.html page you used
<div id="navabout">
the code would then display your about picture, but if you used the navindex it would then display the index picture.
As for uploading files I have never heard of what you are using.
I can tell you this about uploading files...
1.) graphics files must be up/down loaded as a
binary file.
2.) text files must be up/down loaded as
ascii file.
3.) somtimes you have to upload them again, because something got lost in the transmission and then there are times you have to close the upload session, wait 1/2 hour then try again.
Maybe try FileZilla its a open source ftp program works just like explorer.
And did we miss the link to your site?