Denyons, welcome to the Gauge!
I don't know what graphics program you are using to resize your pictures. Resizing to 640x480 pixels is ok, but if a pic contains many details the file size still is too big.
Now when you start saving a pic, you should be able to change some settings concerning the picture quality. Try to find that menu on your program, and then lower the PICTURE SAVING QUALITY. Result: The file size shrinks, although in most cases you can't even see a noticeable reduction of the picture quality! (This shows only in the extremely fine details.)
For all picture conversions I am doing, I use the "Irfan Viewer", an excellent graphics program which can be downloaded
here. It is absolutely free and handles about every possible form of graphics (and even videos and movies). When you want to save a JPG picture, on the up-popping menu there is an option "Show options dialog" which you activate by a mouseclick. Another window pops up and there is a slider to adjust the "Save quality". I found that a setting of 80% doesn't change the picture file size, but going down to 50% already reduces it already quite a bit, practically without quality loss. Two or three times I even used a setting of 20% to post a picture here, and it showed up ok on the monitor. (BTW: If you you go higher than 80%, the file size even gets bigger - although the quality doesn't seem better than before, either!

)
Basically - when you have a picture with many small details, even a JPG picture file turns out quite big. Only when the pic shows big areas in the same color, the compression will be dramatic.
Hope this helps a bit - and good luck for resizing your pics. I hope you'll show us more of your layout which so far looks very interesting!
Ron