The website Embossify has helped me with everything I've needed, it provides great prices for the image sizes and quality.
It shows demonstrations of what the site does, it was created by a man with ambition and knows what he is doing.
You can convert your drawings, creations or what have you into; 3d objects, jpegs into 3d STL files for 3d Meshes for 3d printing, CNC routing, lithophanes, reliefs, or other 3d design elements.
All other sites that I have used personally have failed to bring high quality STL images, except Embossify.