Well, I'll throw my two cents in.
First, there are 19 total lights in the cluster. 6 of these are for backlighting the gauges. Five of them are #194 wedge bulbs, and the other is a #73 microbulb. There is also a 6th #194 for the fuel warning light.
The remaining 12 are #73 microbulbs for: Seatbelt, Door/hatch warning, oil pressure, battery, brake, signal lights, high beam, cruise, check engine, air bag, abs.
Now, so far as replacing them goes:
First, replacing the bulbs with higher wattage bulbs would be an especially bad idea in my opinion. The plastic/copper IC on the back of the cluster is only rated for so much current, and significantly increasing the load on it could lead to burnt traces, or even a fire.
For the six "backlight" bulbs-- these are very difficult to replace with LEDs as they require 180 degree output (like an ID bulb) to work properly. They do not shine directly through the cluster, but rather are there to illuminate a plastic backing behind the gauges. Replacing these with LEDs would probably result in worse lighting overall, unless you managed to find a very broad beam LED. The widest I know of are ~50 degrees or so, which is not enough for these locations without some kind of reflector. Even worse, most "superbright" LEDs are 15 degree.
For the caution and warning lights, these are "straight through" instrument lights, and replacing them with LEDs should work very well. For the record you'd need: 2 Green, 2 Blue, 6 Red and 3 Amber. Replacing these with LEDs is probably a good idea, regardless, as they would be quite a bit brighter, and use much less current, which would ultimately leave more current for the backlight bulbs.
Back to the backlight bulbs: It's possible you could fabricate a LED "bulb" for this purpose with three or four small white LEDs, and aim them in a 180 degree circle around the axis. This would provide sufficient light coverage. However, one should note that if you replace the backlight bulbs with LEDs, your dimmer will no longer work. LEDs do not dim well at all.
Now, if you were going to do it properly, one would have to change out all of the other LEDs as well, including those in the HVAC controls, glove box, et al.