Ricardo Bittencourt has just released Graphos DS, a graphics editor for the TMS9128 video chip, as used in the MSX1, Colecovision and Sega SG-1000. In essence, this editor allows you to draw graphics for the MSX on a
Nintendo DS, showing a preview of the graphics you're creating in the upper screen, and a zoomed edit screen on the lower screen. On the
Graphos DS website you can find out more about this editor and download both Graphos DS and its source code.
Relevant link:
Graphos DS website