Creating a Graphical User Interface in Gimp
Part 1: The line
It's probably the easiest thing to make, and easy to overlook, but it can make a big impact on organisation.
Make a new image one pixel in width, and two pixels in height
Did I say easy?
Get the pencil tool, set to a one pixel brush, set its color to black.
Then just draw on the top pixel of the image.
You might want to scale in a bit to see where to go.
Then set the color to white, and fill in the other pixel.
And that's pretty much it. Its ready to export as a repeating texture.
I'll now show you how it looks in Gimp if you plan on making gui's there.
Make a new larger image, and make the background off white.
Something a little darker than the white you used on the line object.
If you saved the line, you can just take and drag it into the new image from its folder.
It should make a new layer on your new image, and look like the image above.
Make sure you have that layer selected in the layers dialog.
Scale the layer to the width of the new image.
Make sure to only scale the width, and not the height by un-ticking the chain icon.
You can set the interpolation to none, but it really won't matter here.
Then hit scale.
Right click in the layers dialog, and click "layer to image size".
This just lets you see what it looks like without the layer maker getting in the way.
Be sure and experiment with different variations such as bigger widths and heights, and especially opacity.