You can watch DivX movies off the HD, but not in img format. It's been awhile, but I think SMS or My PS2 also has support for it nowadays. According to this link so does PS2realityplayer:
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You can get them all here:
SKS Apps - Wii Ps3 Ps2 Apps - Downloads
You can either burn the media player to disc, and load it that way, install it to the HD through ToxicOS or FTP and boot the mediplayer elf file in devolution mode, which is the way to do it for full HD support. I would try SMS because it's been updated more recently then PS2 Reality Player Pro. Keep in mind the PS2 has an archaic processor, around 333Mhz, so don't expect anything along the lines of Xbox Media Center.