The great thing about being online is the world is your gallery!
One thought is that – as much as people are purchasing your painting, they’re buying a little of you. It’s important that you connect with people on a personal level, whether online or at shows.
I’m not an expert with art sales but have been involved in marketing various businesses and the same principles apply.
Another thought is to add value to your artwork by writing a little about the story, the inspiration, and circumstances around it. Include that with the artwork and also when you’re talking to people about it. They’re buying the story!
Hope that helps!