Every year I hope to carve 1 or 2 geek themed pumpkins. I use the foam pumpkins from Michael’s craft store. I’ve tried Funkins brand which look nicer but found them harder in firmness to actually carve through; but they have better coloring and don’t have messy looking seams.
This year BATMAN was my first pick to carve. The basic process is that if you can’t draw (like me) you find a piece of art you like, preferably simple with high contrast. Take the image into a tool like Gimp or Photoshop. You have to tweak the contrast and reduce any colors (if it isn’t greyscale) to 3 or 4. You’ll have white for cut-out spaces, black for the solid pieces you leave in, and 1 or 2 halfway-cut through styles for shading. There are good tutorials out there you can search for. You have to make sure you don’t have any solid areas left unattached because you can’t “float” them in the cutout unless you plan on working in filaments or something. So even if it looks a little “off” you need more black than you think to make sure all the pieces connect.
See the progress of BATMAN at my blog. Until I migrate the pics, the gallery of previous years’ carvings is at Facebook.