Sprite Stitch Board!

Hi there,
I want to make my sister a great Roberto cushion cover, however my skills at pc-stitch and kgchart suck.
That's why I need help.
It's an evenweave fabric (37x 39.5cms) and I think it's 30-count, i.e. 15 stitches per inch.
I'd like it be really big, hopefully stitching Roberto as big as possible (see the attached image downloaded from google images).
About the colours, well I don't know how many will be needed, perhaps app 10?
I don't care about the background, I think that it will look ok if we leave that blank.
Ah, and last thing, if the great person who could help me out, could provide the *.sth and *.pdf docs, would be wonderful.
Hope someone loves Roberto just like we do and wants to help out. Looking forward to the answer(s)!!!!
Thanks!
Xi

How big are you wanting this? I think I can have it done in a few days.

So I have it done. I changed the colors to what I thought was appropriate but feel free to change them if you don't like it.

The pattern looks good. I think those colors should be ok, I would use florescent for the eyes and mouth or glow in the dark. Depending on what I was using the finished piece for.

Thanks. That was what I was thinking. Plus the color was close to the original so I didn't do much to the eyes but clean it up a bit. I tried putting the picture through PC Stitch but I absolutely hated the way it came out. I would have had to do a lot more work on etting it right in PCStitch than I did with KG-Chart.

thanks knitten kitten for your wonderful help and smash bros for the suggestions.
I'll try to work as speedy as possible and upload an image of the final product.
you guys rock!