Change up the line thickness, you're not drawing with a ballpoint. For example look at the left elbow: the light side, the dark side, and the crook definitely can't have the same outer line. It's got some differences, but the extreme shift in lighting should make it more obvious. You can even drop the outer line completely for that effect.
Check Klimt's sketches for inspiration. There's a lot of subtlety in there. For example check the second drawing here https://artsandculture.google.com/story/XQXhqy-HRypmLQ . The photo/scan is kind of bad, but you should get the idea.
It's a paid product, but for personal use you're only paying for the support or for the number of licenses. The most corporate of all distros offers full functionality for free unlike what op is asking for.
Alien memes