Difficult to say and as I am no longer able to moderate messages I can not check things but can only guess. This is what Imageshack says about sizes/resizing pictures:
i5c13 How do I resize my images using ImageShack?
Select an image to upload, then checkmark the box next to "Resize Image?" Finally, select a new size from the drop down menu and click the "host it!" button. Your image will resample and resize based on the dimensions you selected. However, you cannot resize an image to be bigger than the actual source image that you upload. Your image's original proportions will be kept. Flash and Video cannot be resized.[/color]
So I assume that, when uploading the pictures, you selected thumbnail and that is what you get. Try uploading the actual size as you can always reduce the size if required.