i downloaded trisquel 7 too and the iso is ok
gpg --verify trisquel_7.0_amd64.iso.asc trisquel_7.0_amd64.iso
gpg: Signature made dom 02 nov 2014 19:31:46 CET
gpg: using DSA key B4EFB9F38D8AEBF1
gpg: Good signature from "Trisquel GNU/Linux (Trisquel GNU/Linux signing key)
" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: E6C2 7099 CA21 965B 734A EA31 B4EF B9F3 8D8A EBF1
sha256sum trisquel_7.0_amd64.iso && cat trisquel_7.0_amd64.iso.sha256
ec5be445f9f27b5cace42bc7c454e1a26bf414492da89873cc80dd906fdd073b
trisquel_7.0_amd64.iso
ec5be445f9f27b5cace42bc7c454e1a26bf414492da89873cc80dd906fdd073b
trisquel_7.0_amd64.iso