Photobucket is good i use it all the time, but unfortunately if you want to show higher resolution pictures, imageshack is better. Photobucket has an auto size feature and cuts the quality back slightly, still its good enough really , anyways thats my 10p worth,
Actually ive reread now, go to edit and resize, uncheck keep proportions then you can change it. Mines from photobucket too, the option is there.