To be extremely ghetto about the process, just go ahead and list who you want to see put in the calendar and, if you'd like, who you want to see featured in the same month or, if you're really ambitious, who you want to see in what month.
List of characters to choose from and if you know someone I missed, feel free to say so!
Beatriz DeCosta bwhahahabeck
Tora Olafsdotter ladytalon1
Guy Gardner ladytalon1
Max Lord supergabbie
Ralph and Sue Dibny insomniac_draws
Wally West schwarby
Scott and Barda Free jcho
Gavril Ivanovich cjjoughin
and, just for fun options:
The Injustice League
Power Girl's cat/General Glory's dog
If you couldn't tell, I'm playing this pretty loose as I've never attempted something like this before. But it's for entertainment so no pressure on anyone! Just some fun fanart that you can put as a desktop wallpaper or something^^