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);