Interesting. I thought I had seen the photo in the OP before, and I had. It was used in the Fowler '10 Years of Progress' catalogue, published in 1934.
View attachment 163710
Spot the difference. I think Petters have reused the Fowler publicity photograph and have touched up the photo to replace the standard FOWLER name on the radiator with ACE. Fowler were happy to install whatever engine the purchaser wanted. Most of the early 30 to 45 horsepower locos were petrol or petrol-paraffin powered, along with some alcohol and some diesel. The larger 70hp locos were generally diesel powered. Was it really named ACE or is the assumption of the name based on the doctored photograph?