I would say go for some Cardfight Vanguard characters for them. I can name you a few if you like. Whether it is another character or an unit

Sure, give a characters name.

Kourin Tatsunagi

Yup, that counts for Tea or Yugi or Rebecca.

Either of them would work. If you like, you can go for the entire crew of Ultra Rare. Rekka Tatsunagi and Suiko Tatsunagi

I do like that idea, the trio will become sisters.

Potentially fun one: Twilight Velvet, Night Light, Twilight Sparkle. One happy family!

I would go for Tea as Twilight Velvet, Yugi as Night Light and Rebecca as Twilight Sparkle.

That would be nice! Any MLP family pairing would be interesting really. Or if you're looking for something particularly unique, here's something never done before: two people suiting as one pony, and one person suiting as that pony's EqG counterpart (like a pony Celestia and an EqG Celestia)

Tea and Yugi will be Princess Celestia in her pony counterpart.

Sounds good to me, go for it :)

Pretty much any Animal Crossing character would be cute for Tea. ❤

The characters will be female for Tea to wear as animals.

Yep that's fine lol

For commission ideas, I can draw them for a commission ideas.

It would be interesting of yugi and rebecca cosplay as yugioh monster costumes, killer instinct, pokemon, xioalin showdown or other kids wb show from the 2000's. I am fan of yugioh show as a kid and they are still creative vibe.