Sure. The only thing that concerns me is using the 'attach' function repeatedly for the same picture. You don't have to use the new gallery to get around that, though it is probably the easiest way.
Once a picture is already online somewhere, you can add it using the 'insert image' tool.
This gives you some code, which looks like: {img}{/img}, but with square brackets instead of curly brackets. Right click on the image you want and copy the URL, then paste it in like this:
{img}http://ozpolitic.com/forum/Templates/Forum/default/img.gif{/img}
For hosting images online, you can either attach them to a post and then go back to that post later for the URL when you want to use it again, you can put it in the gallery, which will give everyone easy access, you can get it added to your profile page in the members section, or you can get it hosted on some other website - see the feedback board for more details.