First of all, you're reminded to follow the Images Rules - 2(c).
Here are some image hosting or photo sharing sites that i've been using.
http://imageshack.us/
http://photobucket.com/ (need to register an account to upload)
Other image/photo sharing site:
http://www.flickr.com/
http://www.picoodle.com
I'll show the how-to for ImageShack since it's the easiest to use and most simple to show a tutorial. If you're a first-timer to image/photo posting, this tutorial should give you a basic idea on how to upload and post images on forum even if you're using different websites that might be slightly different.
Click the thumbnails for bigger images and you can zoom for 100% if you can't see the instructions on the images clearly.
1)

2) Copy and paste the appropriate codes at where you want it to be displayed.

To use thumbnail codes, just copy one of the Thumbnail codes and paste in the post.
To use direct link for direct display in post, (got 2 methods)
a) Copy the Direct ink to image and paste in the post box. Highlight the link and then click the Img button.
b) Click the Img button first, then copy the Direct ink to image and paste in between the [img][ /img] code.

Regardless which image sharing websites you use, the method of posting images/pictures in the forum is the same.

