Make a copy of each picture, resized (or cropped) to about 800x600. Upload that copy. Otherwise people either have to pan and scan the picture back and forth to see it all
(very annoying to have to do) or not bother to look at more than 800x600 worth of the picture.
(Actually many monitors are 1024x768 but the Internet Explorer or other browser margins take up some of that space and also some people don't have monitors with that resolution.)
This resizing also makes the picture files smaller so more will fit in your Flickr allotment. Remove the bigger pictures from Flickr as you upload the smaller copies. Keep the original pictures on your computer or on some other on line archiving service.
Some photo hosting services shrink the picture to fit an even smaller rectangle when showing it to viewers saving them the need to slide it back and forth. This also eliminates any benefit of uploading a higher resolution in the first place. So you could downsize the pictures yourself to that lesser resolution (typically 640x480) before uploading and conserve even more space in your account.
Digital camera hints:
http://www.cockam.com/digicam.htm