If you want to add a Drawable be shown during the load, you can add a placeholder:

Glide.with(context)
    .load(yourUrl)
    .placeholder(R.drawable.placeholder)
    .into(imageView);

If you want a Drawable to be shown if the load fails for any reason:

Glide.with(context)
    .load(yourUrl)
    .error(R.drawable.error)
    .into(imageView);

If you want a Drawable to be shown if you provide a null model (URL, Uri, file path etc):

Glide.with(context)
    .load(maybeNullUrl)
    .fallback(R.drawable.fallback)
    .into(imageView);