I was in DEL two weeks ago, in their brand new international terminal (the one that 9W uses for its international flights).

As far as I was able to see, there was only one business/first class lounge in the terminal, managed by a non-airline third party. I was flying CO at the time and was given a pass to access the lounge by the check-in staff.

The lounge itself was quite pleasant - spacious, cold snacks and hot food, wi-fi internet connection as well as PCs provided in the lounge.

Hope this is (at least somewhat) helpful.