So, after my last suggestion regarding the armor stands, I decided to think about it a little more, and I think there are a few things that the server could use beyond armor stand editing. So, I have a few suggestions here. Some are in plugin form (Spigot/Paper) and some are datapacks.
Datapacks:
1) RPG Loot by michael9r9r (
https://www.planetminecraft.com/data-pack/rpg-loot-data-pack/)
This datapack essentially adds, well, some custom loot, with tiers in between (i.e. Uncommon or Legendary) and some custom bosses and enemies. The datapack doesn't actually stray from vanilla, but instead uses the AttributeModifiers command for custom loot. It also has a few custom structures. Due to the way the datapack works, diamond is not necessarily the best choice, meaning we could see come variety in gear among the players. Supposedly, it isn't compatible with other datapacks that alters the vanilla loot tables, but from my testing, it should work with the other datapacks mentioned here. NOTE: The datapack doesn't require fresh chunks. You simply rename a diamond pick to "Ancient Excavator" and throw it on the ground. The pick will disappear and it will immediately spawn in a structure from the pack.
2) Technical Enchant by Hardel (
https://www.planetminecraft.com/data-pack/enchant-datapack-1-13/)
Technical Enchant adds a good amount of new enchantments that can prove to be helpful, as well as a few unique ones, such as Timebreaker. More info can be found on Planet Minecraft. While it works fine with RPG Loot, don't use the custom enchants on the armor and tools generated by RPG Loot. It seems to hate custom attributes.
3) Improved Fishing by DutchCommanderMC (
https://www.planetminecraft.com/data-pack/improved-fishing)
A datapack that alters the loot tables for fishing while adding in some custom mobs (no new models) and custom fishing rods. The datapack is fun to work with and makes fishing a little more flavorful.
4) Expanded Advancement and Recipe Pack by PancakeIdentity (
https://www.curseforge.com/minecraft/customization/platys-advancement-and-recipe-pack)
This datapack adds many new advancements as well as categorizing existing advancements. This allows achievement hunters or people who are bored to do something with their lives. It also adds a couple of recipes, although nothing too broken (unless you consider it adding back the Notch Apple recipe "broken").
Plugins:
1) Crazy Enchants by BadBones69 (
https://www.spigotmc.org/resources/crazy-enchantments.16470/?__cf_chl_jschl_tk__=8d7a9fd0c61a08a20e17ea3479c3b0bfce880a93-1591041533-0-AfzjypY_XBddOSZBW0aXJP_HVmrln2CA-quuCnNhZDClmrLMi99LQ7BVzMuD0uA9Qu3cgcO8RPxWJo74ol_n_HT0yeBnjhCJI3JiqnCfvo_IfXqGL7bh1ZjKO_RdC4bD-S50FkiEfFuU-CXvsC5UFHPDmHZyMEMHYJRjAZ1Gio6tHww_iJHOYhT5Tm8Qra3NWYHFy1FwGGCejOItIZSYdtUzIKQ1INUr_3Yu1Rx3lNYIrC33LQDNJsFq_CLD8JGhfFEfTvDHbfyejU5J6p7y2T91LJAUL0uiHU2A1GSEmWae4ewb1t-y-iv1w7w9b2W9QA)
This plugin adds many custom enchantments that are fairly unique and balanced. It has a few good plugins that it supports, one of the most prominent being WorldGuard.
2) Slimefun by TheBusyBiscuit (
https://github.com/TheBusyBiscuit/Slimefun4)
This one is kind of a weird one, being a sort of techy-vibe plugin. I've seen it receive generally favorable reviews, although some people say that it's a bit tedious and grindy. It does contain 2 other modules, namely Slimefun: Exotic Gardens and Slimefun: Lucky Blocks. It also does have an associated resource pack, although the pack is fan-made and will need to be downloaded separately.