Существует ли вызов API для установки логотипа категории?

[mattdm (Matthew Miller)]

Смотрите

Create a custom badge with an image through the API

Sure, the included badges are … nice. Nothing wrong with them at all. But, what if you want more? What if you want to go beyond the pre-defined symbol set? Sure, there’s an admin page where you can upload them. But what if you want to make a whole lot of badges? Well, good news! You can do this through the API. Here’s Python code showing how it works. (And it awards the badge at the end, for good measure.) This should be pretty easy to read even if you’re not a Python programmer. You can even …

в качестве примера использования нового API загрузки изображений в Discourse. Он предназначен для другой цели, но, вероятно, применим и в вашем случае.