X-Men collage: Filler suggestions and small details

Since im choosing approx. 4 characters for my sleeve and I want the 100% covered with ink, therefor I need something to "flow" behind/between the different characters. Its called filling(i think), but im also pondering about ("small") details from X-Men. This is where I hope my tattoo artist will be able to help me out:)

Fillers:
Elements such as water, fire, thunder/lightning, smoke/clouds,moon, nightsky.


Detail fillers:
Blackbird (X-Mens jet)
Xavier Institute for Higher Learning /  Xavier's School for Gifted Youngsters

 

Beasts eyes, or beasts glasses:

 

Emma frost, I like this full body shot of her, so either that or one with just her face or eyes.

I found this picture on http://windriderx23.deviantart.com/ - amazing artist, I really like this Emma Frost with the whole mind aura going on.

If im not using Gambit as one of the main characters, I would like to have something like this:

And if there's room I want to add a cool "skull", and that would be Xorn's head, potencially awesome skull:)