It sounds like tinypic isn't actually resizing your images for you, they're just hosting them.

You can try using any of of many free image resizing programs such as PixResizer, Picasa, etc before uploading.

Links here:

http://picasa.google.com/

http://bluefive.pair.com/pixresizer.htm

Or you can try using another photo host such as PhotoBucket.com that will resize your images for you when you upload them.

www.photobucket.com