It seems that MakieLayout.jl could help for what you need:
using MakieLayout, AbstractPlotting
using Random
outer_padding = 30
scene, layout = layoutscene(outer_padding, resolution = (1200, 1000));
ax1 = layout[1, 1] = LAxis(scene, title = "My Title")
image = rand(1:4, 64, 48);
image!(ax1, image, scale_plot = false, show_axis = false, interpolate = false, colormap=[:white, :blue, :green, :red])
tightlimits!.(ax1)
hidedecorations!.(ax1)
display(scene)
PS: As a word of caution, I am a Julia beginner and it seems hard to keep track of all the packages needed to do something. In case of Makie there are several in the GLMakie, MakieLayout, AbstractPlotting, etc…