I definitely need to add more uploading options to Screenshot Captor.
Having said that, a main design motivation for me was to be able to support 3rd party tools, and I've tried to make it easy to use such tools from within Screenshot Captor.
So, if you can find a context menu shell extension that can upload files to those services, you can simply right-click on the thumbnail of the image in Screenshot Captor to utilize such a tool.
And/or if you can find a tool that can take a commandline filepath to specify the file to upload, you can configure such a tool for use with Screenshot Captor (and in fact we can share such commandline-tool wrappers).
So the first question should be, are there existing commandline or shell-extension tools for uploading to these services?