Mapstr (Mapstr.gg) is currently a free to use service that allows you to upload your custom and/or procedural maps and have them be served as a direct link for your Rust servers to use. All files are served from and uploaded to an S3 service.
Map uploads are currently restricted to 100MB. We have no intentions of requiring accounts for free uploads unless things get abused, or unless it's a requested feature. Please only upload maps which you own or have the right to use. We will takedown maps which violate this or any part of the ToS.