First of all: General on Griffon! Awesome!
Maybe give hime Hero's sword, it's pretty optimal on Empire Marshal. I'm not sure if the Hardened shield is worth the +1 armour save, I5 is pretty nice. By the way does the Talisman give the whole model the 4+ ward? It does because the griffon is monstrous cav, right? I haven't read the newest version rules properly... The only problem here might be that infantry needs support (Ld, orders) from the General so you don't benefit for having a flying monster. Or what kind of role in your army did you have in mind for your general?
If you play without wizards it's important to have two priests to pray for you. Otherwise the enemy will dispel your most important prayer. It's also good idea to have the Ring of Fire on your Engineer.
The BSB looks a bit naked with just 2+ armour save. I would definitely use every attack possible in close combat to knock him down. Maybe 5+ ward? I know you're most likely trying to pray the ward save for the unit but it doesn't always work out.
50 Spearmen is an impressive unit! Nice! Especially if your general is giving the orders to fight in extra rank and the priest gives them ability to re-roll to wound they're unstoppable. I suppose the 20 halberdiers are going to do good job watching their backs.
14 Crossbowmen with 36" range is an interesting unit. You can use it to threaten the enemy war machines too which is pretty nice. I don't see a reason to take just 14 of them
I'm not sure about the three units of militia. I'm not saying they're not worth taking but I find them hard to see worth taking. 150 points is not a cheap price for ten guys with bs3 and pistols. If you drop the two units of pistol militia you could take three units of rangers. They're scout and shoot 24". But again, I haven't tried pistol chaff. I'm not saying it doesn't work. I'm just saying you're paying a high price for units that are easy to kill with magic, cause panic in your other units and because of the amount of infantry might not be within 12" of the BSB.
The unit of imperial guard is maybe the biggest problem in your army. I really like the greatswords but they die so easily even with the 4+ and 5++. I would definitely try to fit in at least 30 of them. I usually take 35 to exterminate all my enemies. Nothing beats the feeling when you're playing against a strong enemy unit (let's say 10 Chaos trolls or 20 Chaos warriors with characters) and after a successful charge and magic phase you wipe out the whole unit in one close combat round. I don't see that happening with just 22 of them. 10 might easily get killed on the first round and then you don't have enough men to strike back. It is important that the Empire strikes back
I love the Reiters with 2x pistols. They always have a place in my army.
Volleygun and steam tank are good units. Something for your opponents to think about.
Good luck on the battlefield and post us some reports!