Edit:
Important: I made this based on the first limited batch of the Valve Index.
It seems that Valve changed the mount hole spacing after the first batch.
If you have got the newer batch, please use @TENFIRE's modified carrier which should work for you: https://www.thingiverse.com/thing:3863144

As the new Index Wallmounts doesn't fit the HTC Vive's footprint, i remixed the awesome design from @SF3DPrint (https://www.thingiverse.com/thing:2885462)
They grew alot so I had to enlarge the whole base and the sliders.
Height kept the same and so did the hole distances to ensure an easy exchange without drilling new holes into your wall. I added 2 holes in case you need them for first installation.
I replaced the Vive Logo with the Valve Index Logo on both sliders.
I did not have to sand, file, scrape or whatever, it just snaps in without any problems and is a snug fit.
In the photos you can see my first print with 4 holes, but the files supplied have the 6 hole design.

Tip for removing the supports on the base:
Take a flat head screwdriver with a dimension that fits into the groove, put it in, wiggle a bit while pushing and they will break loose and push outside easy, almost without any leftovers.
Make sure it is long and sharp enough and that you don't do it from an angle, just push between print wall and support.