No they won't work because as of this time p1999 only uses 22 different spell gems, but I'm hoping this changes in the near future...
[You must be logged in to view images. Log in or Register.] If you used those files all of your spellgem icons would be in the wrong places compared to p1999.
You would have to move the icons around to match the current default set we have now - luckily enough you can just take the files out of the beta default UI update zip file found on the 'Velious UI' post I made (download the zip
here) because I already did it earlier!. You only need files gemicons01.tga and spells01.tga to match the current system files in p1999.