Just a look at the merchant offerings currently shown on the test server for Halloween 2015. Please remember that this is from the test server, and may change prior to reaching the live servers.
The first group of item are the pumpkin cemeteries that are available for placement on the island, that provide pumpkins. Further information regarding these will be available in other posts. As shown, players can purchase three of each type, and the cost is in game resources.
The next group of items are gem items for purchasing pumpkins and gift boxes, with the prices shown. There are no limits listed.
Other items are special items, with individual limits. There are some new offerings this year, specifically the Lord Dracul general, the Conscientious Geologist, and the Improved Farm.
Other items are returning from last year, such as the grim reaper and village schools
The fish farms, regular silos, improved storehouses are also available this year, with a limit of 3 each. These items are identical to the normal shop offerings except they can be purchased using pumpkins.
The last group of items are unlimited purchases, including resources, buffs, refills, and decorations. New this year is a barracks buff, Nash Williams. Grout is also shown as available in the shop.
More information should be published soon, including the upcoming Sneak Peaks and Developer's Diary. Other information regarding the event quests should be coming soon as well. Please remember that the information here and on the test server may change prior to release on the test server and make game decisions accordingly.