It says in SA EH Siman 62 Sif 8 that there are those who say that you don't need Panim Chadashos (new people) at a Sheva Brachos on Shabbos or Yom Tov (Rishon V'Sheini), since the day itself (in both cases) are like the "Panim Chadashos". This is only, according to the Machaber, at the night seudah and day seudah, but not at Shalosh Seudas. The Rema adds that the custom is to be lenient at Shalosh Seudas and make Sheva Brachos without new people, either because it's usual that Panim Chadashos do in fact come or because some sort of Drush or Divrei Torah are said and that's like Panim Chadashos.
Although it says in Shulchan Aruch Shabbos and Yom Tov Rishon V'Sheini, I want to ask whether there is a reason you wouldn't need Panim Chadashos at a Sheva Brachos on Chol HaMoed in order to say the Sheva Brachos. Or whether there is anyone that speaks about this point.