I have gone through the documentation for TeamCity on build artifact outputs
(https://confluence.jetbrains.com/display/TCD8/Configuring+General+Settings#ConfiguringGene
You can use the following thing when you are using octopack with msbuild to create the nuget package.
The command line parameter /p:OctoPackAppendToPackageId=foo adds foo to your nuget package name. Docs (under publishing)
Example:
Without parameter: abc.nupkg
With parameter: abc.foo.nupkg
ren Release\oldname.exe newname_%build.number%.exe
newname_%build.number%.exe
It is not possible to rename build artifacts using TeamCity. The needed .exe file name should be configured inside your build script.