I don't think so. Good suggestion tho.
The only thing possible for now seems to be importing an image that has a solid color on it.
You can make one really easily with Adobe Draw, or take a photo with the iPad.
There is no "long hold" fill, as there is in Adobe Draw.
Thank you!! How can i do that in Adobe Draw then? Thank you!
make a big square in your comp, then fill it with a long
SSave it to your device or CC
THen use it as your base layer in Sketch
... in case you do not want to do it via importing anything, just paint the layer white.