In order to post pictures to ScrapBook from your cell phone you need to start by making sure that you have set up your ScrapBook account. This ScrapBook FAQ document details how to setup your ScrapBook account.
Setup Post by Email
Once your ScrapBook account is up and running, you will need to set up your account to enable posting by email. This FAQ document details how to set up post by email. Be sure to add the e-mail address of your cell phone to your allowed senders list. Also, at the bottom of the Mobile Post Settings Page you can specify the defaults for pictures uploaded by e-mail.
Creating a message
Now that you've gotten all the one-time setup steps completed you're set to post your pictures! This procedure will vary depending on your particular cell phone. On many phones you can view the desired image and then choose to send it from the options or properties menu that's displayed, or by composing a multimedia message (sometimes called MMS). You send this message to the post.livejournal.com email address, as explained in the directions. (Some people find it easier to save their address with PIN in the address book of their phone, so they do not have to retype it.)
Once LiveJournal recieves your picture e-mail, the picture is stored in your ScrapBook, and a post is created. The default layout is used unless you specify a different layout using the optional image attachment headers in your message. You are also able to change other options using lj-headers.
I'm willing to write simplistic directions for some popular cell phones, if wanted/needed...