Update: E2B 1.63 now supports FreeBSD, pfSense and GhostBSD .img files! See blog post here.
Recent versions of FreeBSD, FreeNAS, PCBSD/TrueOS ISOs do not 'just work' when copied to the E2B USB drive. However, if you can make a bootable FAT32 USB Flash drive that works correctly (e.g. using Unetbootin), then it is often possible to use the MPI Tool Kit's MakePartImage to make a .imgPTN partition image file directly from the working USB Flash drive.
Unfortunately, Unetbootin don't seem to be able to make a bootable FAT32 USB flash drive from recent versions of FreeBSD-based ISOs. These more recent versions can only be booted from a USB Flash drive if they are directly imaged using 'dd' (or RMPrepUSB - File->Drive).
Method for transferring Unetbootin files to E2B1. Using a spare FAT32 freshly-formatted USB Flash drive, use a utility such as Unetbootin to make a bootable USB drive
Note: Do not use the 'dd' method of making a bootable Flash drive as this does not make a FAT32 volume on the USB drive.
2. Test booting from the USB Flash drive on a real system (it may not always work under VBox or VMWare).
3. Drag-and-Drop the USB drive icon (e.g. H:) onto the MPI_FAT32 Desktop shortcut to create a .imgPTN file.
4. Copy the new .imgPTN file to your Easy2Boot USB drive (e.g. \_ISO\LINUX)
5. Run WinContig to make all files on the E2B USB drive contiguous
6. Now boot to E2B and test the new .imgPTN file.
FreeNAS-amd64-LiveCD-0.7.1.4997.img E2B-OK (direct boot from E2B, .img.gz also boots)
FreeNAS-amd64-LiveCD-0.7.1.4997.imgPTN UNB-OK E2B-OK
According to here, FreeBSD 10 does not work with Unetbootin.
FreeBSD-8.4-RELEASE-amd64-bootonly.iso E2B-OK (direct boot)
FreeBSD-8.4-RELEASE-amd64-disc1.iso E2B-OK (direct boot)
FreeBSD-8.0-RELEASE-amd64.iso UNB-OK E2B.imgPTN-OK (direct boot)
So it seems there was a change somewhere between 8.0 and 9.2 which stopped Unetbootin from working...
If you know how to make a FAT32 bootable USB drive with any of these later versions, please let me know! It should be possible to make a working .imgPTN file from it.
Note: see next blog post to see how I got FreeBSD images working.