I know VaVoom can support hi-res textures, but can it support hi-res patches as well? (e.g. menus, fonts, HUD, etc.)

AFAIK Vavoom only has support for Hi-Res textures for now, I think it would be another nice addition if it could support hi-res patches too.

It does, simply put them in <gamedir>/textures/pics.

Forgive me for such a stupid question, but can you, people, explain me what are these hires textures and how I can use them?

The hires textures are images in png or tga format, that allow you to use different colors from the game palette or 32-bit images for textures of flats and walls, there are some packs that add more detail to the original textures for the Doom engine games, you can check J-Files for downloads of these. Also, I'm in the process of packing those textures and upload them to my web space and share the link with you all, heh! I already have the Heretic textures pack ready, it's just a matter of uploading it.

As I understand, these should be located not in WAD, but in specific folder? And then, it might be not very convenient to use them in map editor. You'll have to remember their names and editor will always say that you have invalid texture names on your map.

Even if you use hires textures you need to create the original lowres ones in your wad to avoid map editors give you problems, also, in case people doesn't wants to use them (because of their size). The png or tga image used for the texture must be of the ENTIRE texture, i.e. not a single patch, if you know, in the doom engine textures are made of different patches, this isn't supported for hires textures, the name of the texture should be the SAME name of the whole texture in the wad.

That's interesting, DoomBuilder allows to mix wall textures and flats into one group so you can paste flats on walls and wall textures on floors/ceilings. Maybe that's because it supports JDoom as well.

You can do that in Vavoom too <!-- s;) --><img src="{SMILIES_PATH}/icon_wink.gif" alt=";)" title="Wink" /><!-- s;) -->.

Yes, I am aware of this. That's why I was glad to see that feature in Doom Builder.