I am not familiar with QML.jl (or Qt), but README.md explains the basic usage.
Images, i.e., arrays of colors, could be displayed with display() (via PNG). Images.jl is a collection of packages related to image processing. You could get an array of colors with img = load("image.tiff").
Also, if you convert the color type to ARGB32 (e.g., ARGB32.(img)), you should be able to use JuliaCanvas.
There are many variations of TIFFs, so your TIFF files might not appear as you expect. If you run into problems with reading TIFFs, you may want to create a separate question topic.