I made a png 256x256 and when I went to package I got this:
MainFrameActions: Packaging (Windows (32-bit)): InternalUtils.SafeFileExists: SafeFileExists C:\Users\Slot9\Documents\Unreal Projects\WalkUpAndTalk\Build\Windows\Application.ico=True
MainFrameActions: Packaging (Windows (32-bit)): BuildCommand.Execute: ERROR: BUILD FAILED
MainFrameActions: Packaging (Windows (32-bit)): Program.Main: ERROR: AutomationTool terminated with exception:
MainFrameActions: Packaging (Windows (32-bit)): Program.Main: ERROR: Exception in Win.Automation: Found invalid data while decoding.
MainFrameActions: Packaging (Windows (32-bit)): Stacktrace: at GroupIconResource.ReadIconHeader(BinaryReader Reader)
MainFrameActions: Packaging (Windows (32-bit)): at GroupIconResource.FromIco(String FileName)
MainFrameActions: Packaging (Windows (32-bit)): at BaseWinPlatform.StageBootstrapExecutable(
MainFrameActions: Packaging (Windows (32-bit)): DeploymentContext SC, String TargetFile, String StagedRelativeTargetPath, String StagedArguments)
MainFrameActions: Packaging (Windows (32-bit)): at BaseWinPlatform.GetFilesToDeployOrStage(ProjectParams Params, DeploymentContext SC)
MainFrameActions: Packaging (Windows (32-bit)): at Win32Platform.GetFilesToDeployOrStage(ProjectParams Params, DeploymentContext SC)
MainFrameActions: Packaging (Windows (32-bit)): at Project.CreateStagingManifest(ProjectParams Params, DeploymentContext SC)
MainFrameActions: Packaging (Windows (32-bit)): at Project.CopyBuildToStagingDirectory(ProjectParams Params)
MainFrameActions: Packaging (Windows (32-bit)): at BuildCookRun.DoBuildCookRun(ProjectParams Params)
MainFrameActions: Packaging (Windows (32-bit)): at BuildCommand.Execute()
MainFrameActions: Packaging (Windows (32-bit)): at AutomationTool.Automation.Execute(List`1 CommandsToExecute, CaselessDictionary`1 Commands)
MainFrameActions: Packaging (Windows (32-bit)): at AutomationTool.Automation.Process(String[] CommandLine)
MainFrameActions: Packaging (Windows (32-bit)): at AutomationTool.Program.MainProc(Object Param)
MainFrameActions: Packaging (Windows (32-bit)): at AutomationTool.InternalUtils.RunSingleInstance(MainProc Main, Object Param)
MainFrameActions: Packaging (Windows (32-bit)): at AutomationTool.Program.Main()
MainFrameActions: Packaging (Windows (32-bit)): Program.Main: ERROR: Found invalid data while decoding.
MainFrameActions: Packaging (Windows (32-bit)): ProcessManager.KillAll: Trying to kill 0 spawned processes.
MainFrameActions: Packaging (Windows (32-bit)): Program.Main: AutomationTool exiting with ExitCode=1
MainFrameActions: Packaging (Windows (32-bit)): Domain_ProcessExit
MainFrameActions: Packaging (Windows (32-bit)): ProcessManager.KillAll: Trying to kill 0 spawned processes.
MainFrameActions: Packaging (Windows (32-bit)): copying UAT log files...
MainFrameActions: Packaging (Windows (32-bit)): RunUAT.bat ERROR: AutomationTool was unable to run successfully.
MainFrameActions: Packaging (Windows (32-bit)): BUILD FAILED
This is the icon - it was saved as png and renamed to be a.ico for packaging