There isn't an ISO image download for VS 2017, you download the web installer, then pass it the commands to construct a disk layout for you. Here's the location of instructions to do so:
Create an offline installer for Visual Studio 2017
That page includes instructions for:
- Creating an offline installation layout.
- Installing from an offline installation layout (may not be necessary, see the comments on this instruction).
- Customizing the offline installer.
- Updating the offline installer.
And here's the command line I use:
vs_Community.exe --layout c:\vs2017-community-en-US-offline --lang en-US