it's useful if you have a sketch which resembles as accurately as possible the objective you seek. "Just like the following picture" is merely a reference and not particularly useful to reach your goal.
Can you sketch out with paper and pencil the design you require? If you cannot start with a hand-made work of art, it's going to be nearly impossible to create something using a computer program. If you can create a hand-drawn image, you're more than halfway to your finished design.
Consider that you can take a paper sketch and import the image into Inkscape. Use the trace bitmap feature which will give you a series of vectors that can be edited to clean up the picture.
It's common that a hand drawn sketch will have plenty of artifacts to be removed. Some lines will be too thin to appear, others may to thicker than you desire. If you can trace your sketch with ink or dark marker, your trace results will be better.