HELP!!!!!

So, sadly, it is time to start planning birthday parties around here again...and by 'sadly' I mean that I cannot believe the year has gone by already and that my kiddos will be 3 soon!

But I need some help, I know there are great ways to make your own good quality photo invites and send them to a printer to have them printed...but I need HELP! The kids' themes are Mickey (for Boo) & Minnie (for the Princess) Mouse. I would like to put different elements together on my own and send them to a photo procceser, but do not know how to start or get the background/bourder for the foundation....if there is anyone what would have some insight to share I would appreciate it! Thanks so much!