You need a ISP to upload the photos to first.

From the FAQ pages

How do I add an image to my message?

In order to add an image to your message or your signature, you must have the image already available on a web server. This can be an image on your own personal web page, for example. To place an image within a message, simply use the following Markup Tag:

[image*]http://www.url_to_image.com/image_name.gif[/image*]

(remove the asterisks for it to work)

For example, if you have an image called cateye.gif and its available from your own website at http://www.mywebsite.com/pics, then you would use the following image markup:

[image*]http://www.mywebsite.com/pics/cateye.gif[/image*]

(remove the asterisks for it to work)

You can do the same for your signature. Click the My Home option found on any page. Then, under the Main Configuration heading, click on "Personal Information, email, password...". Look for the Signature box, and enter your desired information, including any images/markup as above.

Note: To keep the forums loading quickly for everyone, it is recommended that you do not exceed 35k for your image size.

http://forums.nitroexpress.com/faq_english.php?Cat=#image