If I remember right, these have a larger light dispersal pattern than a standard LED
http://www.seeedstudio.com/depot/parts-superflux-c-32_18.html
I think they are around 120 or so degrees, so that should work pretty well at the back of the pumpkin.
edit - found this on a different suppliers page "(Flux LED) with view angle from 70degree to 120 degree."