A few ideas of how artillery could be spiced up has recently occurred to me;
Artillery pieces have health bars, once depleted the piece is destroyed, direct hits from other guns can completely wipe out the piece.
Gun barrels of said pieces have a capacity limit. Allowing you to fill the gun with powder charges and shot until the barrel is full to the brim.
This in turn ties into the health bar system; If a piece is loaded with too much powder or too many projectiles ontop of the powder, the artillery piece is dealth damage to its health bar or potentially destroyed with the first shot when fired. If lower impact damaging shots are kept up, the piece will eventually be destroyed by its own crew.
However having a 1:1 ratio of one powder charge and one unit of shot-type, be it round, canister, whatever else is added. The health of the gun will be preserved.
The artillery piece could potentially regain its health over a very long period of time if damaged by its crew or a carpenter could repair it which in turn could take a very long time.
That's about it so-far.