When creating a new style VM in azure via powershell i always use this to specify the image
Set-AzureRmVMSourceImage -VM $VirtualMachine -PublisherName MicrosoftWindowsServer -Offer WindowsServer -Skus 2012-R2-Datacenter -Version "latest"
Presuming you are using an MSDN subscription, otherwise you don't have access to Win10. You can run these commands to get the image
Get-AzureRmVMImagePublisher Get-AzureRmVMImageOffer -Location westeurope -PublisherName MicrosoftVisualStudio Get-AzureRmVMImageSku -Location westeurope -PublisherName MicrosoftVisualStudio -Offer windows
The final command will give you a list of Win10 images (for westeurope), the intermediate commands will help you to find other images along the way (the imageoffer cmdlet also has Win10 with Visual Studio preinstalled) They're useful to be able to navigate around quickly.