Wiring diagram for light switch, GFCI, timer and bathroom fan
This looks correct to me. Key pieces:

All grounds together.
Light is switched and powered not on GFCI. This is normal and generally preferred, with the exception if the light is directly over a tub/shower.
GFCI blank face. My preference generally would be to make use of it as a receptacle for almost no extra cost. However, since bathroom receptacle circuits are supposed to be 20A, while existing 15A receptacles would be grandfathered I think new receptacles would not be. (Changing to 20A would require 12 AWG wire.)
Timer after the GFCI. Note that timer actually probably does not need to be GFCI-protected, unless the fan is over a wet area (tub/shower). But if it is going to be on a GFCI, it should be after (as you have it), not before.

I would recommend using wire nuts and a pigtail rather than directly connecting the timer to the GFCI. That will make any repairs/replacement easier.