How I can delete the lines in this picture?

I have a game called Kaneva is very similar to Sims and Second Life, has been added a new feature that lets you create your clothes for your avatar and I've only started with him and I realized that the model has all these lines, which has a long REALLY to fill all the circumstances, I was wondering if anyone knows of a way to get rid of these lines with the exception of the eraser tool. I only use the GIMP, Adobe Photoshop CS3 and Microsoft Paint. Please help me and thanks! When I fill the thing I want to say I want full color with the click of a button, not only what shirt behind the shirt. Heres what the model looks like http://templates.kaneva.com/M_Shirts_000_UVs.jpg

Don I do not know

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