To build on the answer Vincent provides, with which I totally agree.
I answered a question some time ago that started abstract and slowly got more precise with actual graphic material. Reading between the lines, OP wanted examples to solve his problem. I provided a part of it and then OP added a bounty on the question. I felt like the bounty mechanism could quickly become an incentive to "Will you do my work for me?"
As a teacher, I was also concerned with this question that got a lot of answers, as it became obvious fairly quickly that we were providing almost ready-made answers to OP's assignment, possibly hindering OP's learning process or interfering with the teacher/assignment.
You've been a stellar contributor lately and you obviously put a lot of time in your answers. I think if you get an intuition that someone is looking to get their work done by you, two things you can do:
I don't have that much time so some of my latest answers have been
hand sketched. While hand sketching is not applicable for the technical
questions, it does somewhat ensure that the OP is doing their share
of the work when the question has a more symbolic or artistic
orientation.
You could answer but try not to provide the exact end result the OP
is looking for. Maybe you change a color or tweak a superficial
detail a bit so that the OP actually has their answer but needs to create their own thing with their specific requirements and not just grab a file from your answer.
This question from Mathematics meta can also provide some
inspiration.
ETA: If you do get to the point that the OP requests a file from you, don't feel obligated in any way to oblige them. A serious participant to this site will either not ask or learn quickly that this is not what we are here for.