Yeah, I also had the thought of inserting one or two Gungans among the Resistance. You could take them from Gungan Alliance scene from TPM and put them in the background of one of the Resistance briefings.

It could be cool to swap out the head of one of the human Resistance members with a Gungan, so they could be wearing Resistance garb. Maybe you could use Jar Jar’s head, since it is a little higher quality than background Gungans, but recolor it slightly so he looks like a different Gungan.
But if they’re in the background, you could just blur them slightly to better hide the 1999-era CGI.

If you combine the ROTJ and TROS celebrations, you also could stick the Naboo shot in right before it cuts back to everyone returning to the Resistance base.