Existing: There's a few things I think could be altered to the existing festivals.
Spring: Should come slightly earlier in the year. Perhaps should reward non-dyable cosmetics (IE: Red and white heart dresses/cloaks/robes) and special furniture (Pink wicker anyone?)
Summer: Maybe the reward for complete all the firework deeds is getting a kit/skill that allows you to build your own 'firework shows' (5-10 fireworks that you can shoot off timed as you wish).
Farmers Fair: How about a contest to see who can grow the best . This could be a player-interactive game where you must follow certain steps to 'grow' the vegetable, the better you do at the steps, the healthier the vegetable, the higher the score! It could reward tokens for second place, and special furniture or cosmetics for first.
Fall: Trick-or-Treat in Bree land! There are a thousand and one doors in Bree. Maybe add some NPCs behind them and have players go trick-or-treating! This could reward sweets that could be used to barter for special items.
Treasure hunt: The idea is great, but the incentive is lacking. Maybe add in more rewards? Possibly ornate clothing in the huge boxes?
Winter: The winter festival is probably my favorite. But all the same I would love to see it added to. Maybe add some new seasonal items? A greater variety of scarves (stripped, plaid) as well as mittens, ear muffs and so on. How about a steaming cup of tea as a hand held? And best of all: more seasonal housing! How about fireplaces, identical in base to the existing ones, with brightly colored stockings over it? An indoor Christmas tree or two? Mistletoe to hang from the ceiling?
Now how about you add in a 'Market week' in Bree. This could be an event in the Square where limited-time-only vendors selling their wares (Clothing, housing items, war-steed cosmetics, maybe even PvE items such as jewellery and cloaks with stats) appear. But, oh my! They only want to barter! So what you do is make temporary crafting recipies available uniquely for each crafting proficiency. These allow you to make items that you can barter with. However not all vendors accept all forms of currency! This could involve trading with other players to get the right type of bartering item.
Also a great addition would be to add in drinking contests in the main inns during festivals. Winning these could bestow titles such as 'Mead-bellied, Holder of Ale, Drainer of Mugs' and so on. As well as ornate hand held mugs and drinking related housing items. (Like tables covered in mugs and spilt ale).
[B]Crickhollow:[/b] Evandriel, Elgilleth, Rathrilwing,
[B]Landroval:[/b] Lelyaruivë [Fueled by Rum and Spite], Dalflen , Zanyadel
[B]Laurelin: [/b] Silmacalë
[B]Creeps: [/b] Landroval: Ellianakh (warg), Ellianokh (defiler), [Rage Against the Freeps]