The commission slots are a fixed price, as such the quality of the picture might vary depending on how much is in the picture! A bust of a single character might be a lot prettier than a fullbody piece of three characters interacting, since I have to allocate the same amount of time to them! (Generally two characters is a good limit, but I can do more depending on how much of them are visible, how detailed they are, etc.)
In addition, the commissions from Substar have priority in the commission queue!
Also for reference, attached is the normal stream commission prices and terms!
If a tier is ever full, feel free to DM me to ask if I could raise the limit. Trying to take it slow to make sure the workload is managable!