For those who aren't terribly artistic, and can't find quite the embroidery pattern they want, the idea of making their own can also make them cringe. But all you need is the ideas, the image that you want to reproduce, some white tissue giftwrap, and a transfer pencil.
Let's say you want to embroider panels for a baby quilt, and you have a children's coloring book with figures that you'd like to copy. Tear out the page, and cut a piece of the white tissue that is slightly larger. Lay the picture face down on the tissue and tape them together. Now turn the picture/tissue over, and you'll be able to see the lines of the image through the tissue. Trace over them with the transfer pencil, then remove the tape.
Take the tissue paper design and lay it face down on your fabric. Use a dry iron set on low, pressed to the paper for a few seconds, then lifted and pressed on another area of the tissue. Try not to "rub" it back and forth as that can smear the transfer. You might like to try the technique on a piece of odd cloth to be sure of your technique, first.
Now you can just embroider along the lines, which will be pretty much covered by the thread. If not, all you need do is wash the square after, or wait until the entire quilt top is done, and then wash the whole thing to remove any obvious pencil marks.