Hello!
Sorry for the late response! Here's my tutorial for making art in a textbox.
1. First, in the Pixel Editor, open your HUD tiles and choose some tiles that you don't plan to use.
Draw a picture in those tiles. Here I've used 4 tiles near the end.
2. In HUD & Boxes: Define your "USER" tiles to be the ones you drew your picture in.
USER_0 is the first tile, USER_1 is the next tile, etc.
3. In TEXT: Arrange your "USER" tiles together like puzzle pieces in the textbox
Here, I've placed my 4 USER tiles to the left of my other text.
4. Your picture should appear in your text box!
Now, you could use other tiles to make more pictures. But of course, the more tiles you use for pictures, the fewer you have for text. You could make small single tile pictures. I'm sure people will find creative solutions!
I hope this helps!