In pyplot this is simply ax.set_xticklabels([tick positions], [tick labels (strings)]).

scene = plot(..., ticks = (ranges = ([0, 1], [0, 1]), labels = (["a", "b"], ["a", "b"])))

should be possible to pass a node to ranges/labels a la ranges = Node(([0, 1], [0, 1]))

Your suggestion doesn't work even without Nodes. I don't seem to see any tick labels updated:

scene = scatter(rand(10), rand(10), ticks = (ranges = ([0, 1], [0, 1]), labels = (["a", "b"], ["a", "b"])))

Here is the code that does what I want:

limits = FRect2D((-5.0,-5.0),(10.0,10.0))
w = scatter(rand(10), rand(10), limits=limits)
display(w)
w[Axis][:ticks][:ranges] = ([-5,5], [-5,5])
w[Axis][:ticks][:labels] = (["A", "B"], ["A", "B"])

But unfortunately doesn't work with observables at the moment. That would be cool though!
E.,g.:

xlab = Observable(["A", "B"])
w[Axis][:ticks][:labels] = (xlab, xlab)

gives

MethodError: Cannot `convert` an object of type Observable{Array{String,1}} to an object of type Array{String,1}
Closest candidates are:
  convert(::Type{Array{String,1}}, !Matched::LibGit2.StrArrayStruct) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\LibGit2\src\strarray.jl:14
  convert(::Type{Array{T,N}}, !Matched::StaticArrays.SizedArray{S,T,N,M} where M) where {T, S, N} at C:\Users\datseris\.julia\packages\StaticArrays\mcf7t\src\SizedArray.jl:80
  convert(::Type{Array{T,N}}, !Matched::AxisArrays.AxisArray{T,N,D,Ax} where Ax where D) where {T, N} at C:\Users\datseris\.julia\packages\AxisArrays\G6pZY\src\core.jl:295
  ...

Yeah, that's not how you'd use observables... You need to pass the observables to the plotting function...
If you want to use your way, you'd need to do:

xlab = Observable(["A", "B"])
on(xlab) do xlab
    w[Axis][:ticks][:labels] = (xlab, xlab)
end

Alright, this is satisfactory for me. Could you please put a "documentation" label on this one? Seems useful enough to be in the docs.

By the way this is in my opinion the preferred option:

using Makie

ranges = Node(([0, 1], [0, 1]))
labels = Node((["a", "b"], ["a", "b"]))
function to_limits(lims)
    xy = (lims[1][1], lims[2][1])
    xymax = (lims[1][2], lims[2][2])
    FRect(xy, xymax .- xy)
end
w = scatter(
    rand(10), rand(10),
    axis = (
        ticks = (
            ranges = ranges,
            labels = labels
        ),
    ),
    limits = lift(to_limits, ranges) # really unfortunate we 
)

TODO: automatically calculate limits from the ranges instead of the data + have limits work with the ranges format in general!

To set alignment:

w[Axis][:ticks][:align] = ((:center, :top), (:right, :center))