There is native hercules support in the sampler on the linked page, which is probably the source of the screenshots.

The earliest intepreter version for Loom that I have (3.5.37), with code protection, does not have native hercules support. The earliest intepreter version for Secret of Monkey Island that I have (4.0.62), also released in 1990, does have native hercules support, but the support was dropped in later interpreter versions. So it seems the native support was kind of hit-and-miss.

Yes.. ripsaw.. i don't notice the download...

mmm... Loom 3.5.37 that you said, and 3.5.40 (interpreter release for EGA version) don't have Hercules support..
But the sampler has the same Interpreter version that Monkey Island, which is 4.0.62

Maybe after initial release of Loom they release a Hercules version with the newer version of the interpreter... don't know... and i don't remember...

I took pictures for comparison on real hercules machine

Release Version (use interpreter 3.5.40) with CGA MODE - SimCGA previously loaded

Sampler Demo Version (use interpreter 4.0.62 same version as Monkey Island) with HERCULES MODE

Hercules has better detail (resolution i suppose), the tree is an example. The character was taller... i prefer this size.
CGA is looking better than hercules on the uniform colors, the clothing of the character is an example... but CGA has some ghosts during interlacing in scroll, more noticeably on the intro when the nymph moves from the village to the tree...

....

I have seen every English version of the retail floppy version of Loom and none of the interpreters have Hercules support. Loom also uses 3.5.37 as well as 3.5.40. Indiana Jones and the Last Crusade: The Adventure Game, also uses a v3.xx interpreter and it does not support Hercules either. Unfortunately I sincerely doubt you can use an interpreter from a different game to obtain the Hercules support.

The title screen is not identical between the Sampler and the Full Game, but here is a comparison between the two :

And here are some in-game graphics :

SimCGA adjusts the CRTC registers to get a more CGA-like resolution of 640x300, Sierra SCI games do this as well. SCUMM games do not adjust the registers but otherwise the resolution stretch is the same and they stick their upscaled graphics in the middle of the screen. Upscaling algorithms differ, and Lucas' looks a little nicer.

Thanks for the response... i suppose that the hercules version doesn't exists...

Neither 3.5.37 nor 5.1.42 CDROM have got Hercules support.