Well after about 10 years as an illustrator, I've got boxes of originals. I left an entire box of them at the house I moved out of a few years ago. In the attic. That's where I still keep the boxes of originals that I have now are-- in my attic. Just so you know.
My working illustration process just doesn't generate heirlooms right now. Oh well, maybe someday.
My advice to the potential art connoisseur is to amass a collection of ballpoint pen drawings. You can ask to be buried with them when you die, and no one will care because they'll all look really bad anyway.
After I finished the ink work, I scanned it in (actually in two parts -- it's on an 11x17 piece of copy paper) and colored it up.
I use Photoshop and a graphics tablet of some sort to color stuff up. When I did this piece, I used an Intuos 3, but I have a crappy Cintiq that I got off of Ebay for about half price. I adjust the "Levels" to brighten the white of the paper and darken the linework a little. I have the drawing on a "multiplied" layer sitting on top and subsequent layers of color underneath. I always try to preserve a digital copy of the original drawing.
I really liked the "original" piece I did for this drawing. Super busy. Lots of stuff going on. Fun to look at. So it's in a drawer in my filing cabinet with a bunch of brother and sister drawings. They keep quiet for the most part, but sometimes I open up the drawer and it's apparent that something had to have been going on in there. Some kind of party. I never leave my drawers that messy.