They may appear gray, but they can be loaded in game.
So to see them in HVR, you need to, when opening a map OR clicking Map Options
(F2) when you load a map, go to where it says Add Resource
, then add your PK3
with all your textures in it. Same goes for adding any of Ring Racers' textures, which are found in the data
folder.
However, if your textures still appear gray, even ingame, then perhaps it may have been a conversion error. Make sure you've converted them to Doom GFX under the SRB2 palette!
EDIT: I see you have taken these from the community texture pack. These were made for vanilla SRB2, so I'm unsure if you need to do anything different to get them looking right in Ring Racers. While I'm sure the latest version of SRB2 uses the same palette as Ring Racers, there may have been something I missed. Ring Racers doesn't use Doom Flats anymore, so check if there are any Doom Flats, and convert those to Doom GFX.