Thank you @veta-less for taking an interest in this contest and for your nice question.
You can use a graphite pencil, or other materials like, charcoal, sepia or chalk if it's a stick/pencil of that material.
I hope that helps and I look forward to seeing your posts.
Thank you very much for the answer @livvu!
I am glad that I can use different materials for graphics.:) I will be happy to participate in this contest)
It's my pleasure! Thank you for your contribution @veta-less