Configuring build.lua to install images

I have a bunch of logos I want to package up into a module within a LaTeX bundle. But my build.lua file won’t install them.

I have a subdirectory logos a the top level of my bundle. In that directory, I have many images in EPS, PDF, SVG, PNG, and JPG format. I have one documentation file logos.tex which is supposed to include them all. My build.lua has these variables set:

bundle = "mybundle"
module = "logos"    
maindir = ".."

installfiles = {"*.eps", "*.svg", "*.pdf", "*.png", "*.jpg"}
tdsroot = "generic"
typesetfiles = {"logos.tex"}
typesetexe = "xelatex"
cleanfiles = {"*.log", "logos.pdf", "*.zip"}

I can compile logos.tex manually within the logos directory. But if I run l3build install, nothing happens. And if I run l3build doc, the compilation fails, because the images aren’t being copied over to the build directory.

What am I missing here?