Can you use ASE models in Quake 4? Yes. All of the default content for Quake 4 are either LWO or MD5 model files but ASE do work. Just open the ASE file into NotePad or similar text only editor and edit the *BITMAP reference in the ASE file so it looks like the following;
//q4base/[material]/[path]/[here]
The important bit is '//q4base/' which is what all paths are relative to. It's actually the same as ASE in Doom 3 but Quake 4 uses 'q4base' as the assets root directory. Technically you can use anything after q4base/ so long as you reference the material correctly (and the texture assets within the material are correct), make sure your use of '/' or '' point the same way in both the ASE and the material; writing //q4base/models/' is not the same as 'q4basemodels'.
Your actual material file, which the ASE is referencing, can technically be anything you like but, you might find it easier from an organisational point of view to write your material shaders similar to the following;
models/mapobjects/[mymodel]/[model_image_ref]
Note there is no need for the *.tga file extension in either the ASE or the material references, those are used to directly reference textures further down the materials stages.
General note for ASE models:
The texture you apply to the model in Max (or any other 3D app) should be treated as a place holder, a temporary texture, so all you need to worry about is the UVWmap and getting that scaled correctly relative to the texture image (hopefully you will have used a standard 256x256, [power of '2' (x2) sized texture] etc.) and the physical size of the object.
3D application material settings
One note here that often crops up;
In your 3D app you only need is a base or basic material and the models UVWmap for ASE models to work; Quake 4 does not make use of any 3D application material settings like 'tiling', 'opacity' or 'alpha' maps etc.; it's just looking for the UVWmap (or vertex colours when texture blending) and a base material.
