Oh. Got it. Thanks.
For anyone not able to check/uncheck "Use Textures", your problem is the app is not finding your textures folder.
This is the workaround I used:
1. Uncheck "Autodetect texture folder" on the "Settings" dialog
2. Manually set the textures folder to "[...]/Terraria/Content/Images"
3. Uncheck "Use Textures" in case it's already checked (came selected by default for me)
4. Check "Use Textures".
After a few milliseconds of load, textures should now display when zoomed in enough.
Oh, I really didn't pay enough attention to the numbers, my bad.Wait, so there's a new hotfix coming and Terrafirma got updated?