Normally photoshop elements does not allow the user to save new document presets.
You can add presets to the new document dialog by editing the new document text file, but that's a pain.
This script (Create New Canvas by Paul Riggott) will save document presets and you can also add guides. However you always need to use this script to access
the presets, they won't show in the File> New> Blank File dialog. (this script should work in pse 6 thru pse 10)
(the only thing that won't work in elements is the cmyk setting)
1. download and unzip the file
2. right click on the script and choose Copy.
3. Go to the pse 10 scripts folder, right click in an empty area and choose Paste.
windows x64 systems:
C:\Program Files (x86)\Adobe\Photoshop Elements 10\Presets\Scripts
windows 32 bit systems:
C:\Program Files\Adobe\Photoshop Elements 10\Presets\Scripts
I'm not sure of the exact path for a mac system.
4. Start or restart pse 10 and the Create New Canvas script should be listed under File>Automation Tools.
To create a new preset, press Add New canvas after opening the script, enter the info and then press the Add canvas button and the preset should be listed in the Create New Canvas dialog.