it would be nice to be able to set the program to download the maximum available size of the selected pictures.
or to have an option that let the user decide which default dimension to download (Original, Large, Medium)
the original picture has a different postfix after the id* in the URL, so some extra steps are needed to get it (but not too difficult).
e.g. URL of a nice pic:
All Sizes link (by default goes to the l = large one):
To get the original size picture link:
medium size picture:
large size picture: http://farm2.static.flickr.com/1213/1380934090_4ced50dd37_b.jpg
original size picture:
As you can see it's quite easy to build some functions to get ther html page of the original (if it exists) and from there retrieve with a regular expression (or whatever) the link to the maxium size picture.