The background looks great so far. Nice job. You can keep a pair of D. Auratus safely in an enclosure that large. I'd be careful with keeping more. The females tend to be very territorial and can be aggressive towards other females. If you do decide to keep a third try to ensure that at least 2 out of the three are males as they tend to be less aggressive. Make sure you include some good tall branches etc for climbing as they love to climb high when they call.