Glad you are enjoying your experience here on steemit! I understand how it is with old pieces, I have the same situation where I have many old pieces and I made them long before I ever considered documenting any process. What I've done with those is to discuss how I work, shown photos of my work space, or a show they were in. My work also takes forever to make so I don't have too many to show.
It's great to show photos of your studio or talk about how you work or anything that may be useful for you to discuss! The point is to create more of a story that people can connect with and that interests you. I know as artists we're taught that the work should stand alone, but here on Steemit, it's a blog platform rather than instagram or facebook type social media so we want to know more - more personalized, more of a story.
You should certainly do you are most comfortable with and I certainly don't intend to be pushy, only helpful! My suggestions are simply because I see you are talented and I would like to see you earn more for your work. I wish you the best and will keep my eye on your blog! Cheers
Thank you very much for your advice, you are very kind. I will do as you say. Today I will make a post of a painting step by step. Regards!!