A plainly named helper for adding stickers to existing packs — a narrower companion to the official Stickers bot rather than a full replacement.
Alternatives to Stickerizer
Bots from the same subtopic ranked by our score, plus hand-picked options.

An inline bot that mashes two emoji together into a single custom sticker-style image — type it right inside any chat's message box, no need to open the bot itself.

Telegram's official bot for creating sticker and custom emoji packs: upload images or videos, assign emoji, publish a pack link. Free, no watermarks, no third-party apps.

An open-source bot that converts between Telegram's own message types — turning a file into a voice, video, photo or sticker message and back, with the source code public on GitHub.

An open-source resizer purpose-built for one job: preparing images to the exact 512px specs Telegram sticker packs require, with the code published on GitHub.
A general-purpose 'factory'-branded sticker creation bot — one more confirmed-live option in a crowded niche of third-party sticker makers.
A generically named sticker-creation bot — another confirmed-live option to try alongside the more distinctly featured bots in this list.
A cheerfully named sticker bot — presumably cat-themed given the name, and a confirmed-live option to round out this list.