Label tiles are included in the next upcoming beta.
In the meantime, some people use media tiles with Shields.io to create text placeholders.
For example, the following URL creates the following text (which is a scalable vector graphic):
And looks like the following when formatted in a tile:
The concept can be used more broadly to integrate data from third party JSON sources as shown in this thread:
The nice thing about it being scalable is you can resize your base tile size to whatever you want. Some people will cut their base tile size down to 1/4 the default (40px) and then quadruple the dimensions on all their other tiles to bring them back to ‘nornal’. That lets them use extra small tiles wherever they please for things like these labels.