Add design after completed W.I.P?

Sorry about the title,I tried to make it as short as possible. To make my question more understandable…I have just completed my very first original knitted piece. Now I want to add a design onto it but am not sure how to do that or what technique is best. The piece is done in garter stitch. I started this project with the idea of adding the design last instead of while I was knitting. I am pleased with my results thus far but am stuck at this point. I am a somewhat newbie to knitting . Thanks in advance for any and all help and advice.

What you’re referring to is called duplicate stitch or Swiss darning. I’ve seen instructions for stockinette, but not for garter. Maybe a more extensive Google search than I did will come up with something.

Duplicate stitch in garter will look a bit odd, I would just embroider it but what kind of design is it that you are after?

its so cool that your a newbie and are trying to make you owne pattern well done you! maybe u could icord something on http://www.knitty.com/ISSUEsummer03/PATTdaisy.html like this? what is it that your making can i see? i cant think of how eles you could change it but im sure someone will help you.

I slept on it and came up with an idea to use for the garter stitch. Had I known before I started I would have went the other route so that I could use the duplicate stitch.But I am going to try and make more that way also. I am sorry I can’t tell you what it is I am working on because 1) it is my own pattern and I don’t want anyone to run across it, make a couple of changes and claim it as theirs and 2) I hope to make a little spare change to help out with household needs.
But who knows how it will end I may end up posting it as a free pattern. Thanks again for all the help.