Designs - In your....?

Once you start painting lots of designs, do you keep them all in your head or do you just know what to do?

Like if someone asks for a video game character, do you have a cheat sheet, design page, etc to remind you how you do it, or do you just wing it?

I've been doing everything from memory, but sometimes I realize that I missed a detail that would really make something pop! I don't know if it's just my inexperience or if anyone else has that problem and if they have any work arounds.

I am really trying not to have design boards, as I like doing whatever the kids want LOL!

The more you do them, the more "into" your head they become. But, after a long season off (like the winter months or when a design isn't chosen for a while), I will often have to refer to the photo for a few seconds. And sometimes I leave something out and it hits me on the drive home from the festival and I'm all "arrrrrrggggghhhhhh" while at the same time, the child is probably already washed and in bed!   And if I get a request for something I've never done and feel I can't wing it, I will ask them to get a photo of it on their phone.

I like to keep pictures of my designs on my tablet and set it so the screen doesn't shut off, then have it facing me while I paint.    
Design boards don't work for me either because kids get so fixated on certain parts of a picture and if it's not exactly the same they can get disappointed.  There's no greater buzz kill then a kid not liking your painting because it's missing one stinking dot somewhere.

I have 5 sample sheets: girly/pretty/princesses
super heroes/villians/scary stuff; animals of all sorts; sports; cartoon/movie/comic characters

If it's a design I don't do much, I sneak a peek. If it is not EXACTLY the same as the photo, I explain to the child that every masterpiece is an original!