Figured out the problem: I had two copies of the game installed to run MultiLaunch and it seems that the copied version was the system's default version. Which means that when I ran -image, it updated the copy (I run -image with a special shortcut), and then when I then ran Texmod, selecting the original version, that version hadn't been updated: hence no Texmod support. I uninstalled the copy by mistake (I thought of running a fresh install and the game uninstalled the copy instead of the original) and when I ran the original, the first thing it did was to download the update.
As soon as I figured out what happened, I also remembered that the same thing happened to me already before, I just completely forgot about it.
Thanks anyway. ^^