How very ironically fortuitous, modsr, that you have posted asking for ideas about an adventure to the Beacon-Tower. Because I just finished Lore-mastering my group of players through an adventure that I wrote - my first ever - which took them through the Heart of Mirkwood and into the Beacon-Tower, and I've been thinking about how to work up the adventure to share here on the Forum!
My adventure is titled very imaginatively
Into The Woods (sorry, couldn't think of anything better

) and it begins with the party in Rhosgobel or Woodland Hall, where the players have been approached by Bofri son of Bofur, who asks them to accompany him into Mirkwood on his quest to search for the remains of the Old Forest Road. They meet with Radagast and get his advice, and he introduces them to the River-Maidens. The party borrows boats from the folk of Black Tarn Hall, then they row up the Dusky to its headwaters in the Haunted Hills. They must find their way through the Heart of Mirkwood, fight off the Giant Spiders, Explore to find the remains of the Road and the Tower, and fight off the vampire bats that live there to get in. Then they must explore the ruins and solve a riddle-puzzle to get into the hidden Treasury, deep beneath the ground level of the remains of the Tower. After finding the contents of the Treasury, which include silver and gold coins, jewels, superior items of wargear, and a small chest of mithril ingots, they exit the Beacon-Tower and are assaulted the next night by a Wood-Wight before fleeing for their lives back to the headwaters of the Dusky.
I currently have four player-heroes: Grundwald, a Woodman Wanderer; Magni, a Barding Warden; Pira, a Dwarven Scholar; and Alistair, a Hobbit Treasure-Hunter. Another player recently left the game, but we've decided to keep her character Miriel, an Elven Scholar, in the party a little while longer. I'm taking them through
Tales from Wilderland; they've been through the first three adventures and the one I wrote, and next session we'll take up TfW again with 'Those Who Tarry No Longer'.
This TOR campaign is the first time I've ever run an RPG, and that combined with the fact that this was the first adventure I'd ever written made me pretty nervous, but it worked out really well. There were things I'll change, mostly about the combats, but I had fun writing the adventure (althought it was a tremendous amount of work) and the players had a blast going through it. They said it was challenging enough to make them feel really good about overcoming the difficulties. I quite naturally tailored my adventure to my players and their characters' situation and interests. The party had traveled to Woodland Hall after 'Of Kinstrife & Dark Tidings" so Grundwald could fulfil his oath to return Wolfbiter to his people. Pira is a female Dwarf, and her player wanted a romantic interest for Pira. Who better than Bofri? I knew he would be at Woodland Hall, and naturally they would meet.
Have you ever had the experience of writing about a character you know, or thought you knew, and have them surprise you with ideas or characteristics of their own? Earlier in this campaign, I'd had Pira's patron Gloin write her a letter, and to my surprise, he turned out to be quite religious - he ended up mentioning his prayers to Mahal (the Vala Aule, creator of the Dwarves) no fewer than four times in that letter. Well, as soon as I started writing about Bofri's introduction to Pira, he had a very well thought-out plan for traveling into Mirkwood to find the remains of the Old Forest Road and the Beacon-Tower. He had used his Specialty of Map-Making to copy an old map of the Road from the library at Erebor, and King Dain had given him a wonder of technological achievement from the Second Age - a compass, which I decided would give him a +2 to his favored Explore 3. (I used his outlined stats from Heart of the Wild, and expanded them into a full character sheet, since I knew he would need weapon and other skills.)
Like I said, I wrote the adventure for these characters in this situation, so I'll need to do some (un)tailoring to make the adventure applicable for other parties. And since I'm a visual sort of person, I planned out the Beacon-Tower on graph paper, so I'll need to find a way to include those plans in my final adventure. But if you're interested in more detail, I'm happy to discuss it more!