I do not own an iphone but do use openbsd to load music files to a portable mpg player. The methods should be similiar.
I would start by connecting the iphone via it's cable (usb vs firewire?) to the OpenBSD system and
running
dmesg(8)
If Apple has not crippled basic connectivity you should see a new sd* device at the end of the dmesg.
The OpenBSD FAQ has instructions on how to
mount devices. If you are successful, you should be able to change to the mount point directory and browse until you find the iphone directory containing your images.
I also found this older link regard using
ssh(1) to wireless access iphone pictures.