您可以使用azurerm_client_config和lookup function数据源：

variable "vm_template" {
      type = map(any)
      default = {
        vm1 = {
          prd_source_image_id = "prd_image"
          dev_source_image_id = "dev_image"
          default_image       = "default_image"
          }
      }
    }

    variable "subscriptions_to_env" {
      type = map(string)
      default = {
        "aaa-111-555-etc" = "dev",
        "111-aaa-999-etc" = "prd"
      }
    }

    data "azurerm_client_config" "current" {}

    locals {
      current_env = lookup(var.subscriptions_to_env, data.azurerm_client_config.current.subscription_id, "None")
    }

    resource "azurerm_linux_virtual_machine" "vm" {
      for_each = var.vm_template
    ...(omission)
      source_image_id     = local.current_env == "dev" ? each.value.dev_source_image_id : (
                              local.current_env == "prd" ? each.value.prd_source_image_id : each.value.default_image
                              )
    ...(omission)
    }

注：建议使用默认镜像（prd、dev或其他），条件如下：

If env is dev: image dev
else if env is prd: image prd
else image default

如果对你有帮助就告诉我