Hi there,
No-one is blocked from adding a file to each post (well, you have to be a registered member). What may be the problem is the seize of your photo, do you know the dimensions and the seize (megabytes) of the photo that you would like to add? If it comes straight from the camera you most likely need to re-seize it down.
In case you have problems with the process of attaching a photo (this also works for word documents and pdf documents as well) here are the steps:
1) When you are typing your message, scroll down to under the text box where you are writing.
2) Click the "Upload attachment" tab.
3) Click "Browse" and select the file you would like to upload.
4) The click the "Add the file" button (wait a few seconds for the file to be uploaded).
... now when you click the "Submit" button to submit your message this file will be added to your post.
Note: If your file is too big, you will get an error, I think in step 4.
Please let me know how it goes.
Un saludo from Santiago,
Ivar