I have not mauch experience with Empire Army in WHFB, but I think some of my suggestion may be handfull.
Look like your opponent overhelm you with
1. Melee units.
2. Magic phase.
3. Warmachines amount.
Looks like he use ALL advantages of the Greenskins army.
But you list looks like did not use advantages of the Empire.
Suggestion to the tactics -
1. SHOOT as much as possible. Take many shooter.
2. Try to hold and slow opponent army (they are always slow due the animosity)
3. After entering into melee - pray and say CHARGEEEE to your knigths units and HOLD THE GROUND to the infantry.
4. Kill the shamans or pray for miscast.
Unit suggestion (without any "fluff"):
Heroes.
1. Drop the pegasus. I think the better choice may be captain BSB for the one of the your infantry units with banner of Sigismund.
2. Think about taking GradnMaster as Lord, not the Elector. That add to your knights more destructive power.
3. If you leave the Elector, you have two choices -
a. With unit of greatswords with Griffon Banner.
б. With your IC knights.
3. Think about change one of your wizard to the warrior priest of Ulric. Overwise, all that you can do with your magic - only dispelling. But priest add you some combat power + bound spell + same dispel dice + hate ws goblins. If you take the priest - of course join him with one of your units.
Core
1. For the handgunners I prefer repeater rifle, but hochland is good too. May be you can drop one of the unit of handgunners. You should positioned them in 1-rank line, and I think that 30 handgunners + your other troops is too wide (except awesome hilll on your quaters).
2. Drop hallberd and free company
3. Drop one unit of swordsmen (may be even two). 24 - good size for them. Use released swordsmens as detachments.
4. One unit of sweet core knights?

Why?

Take at least one more. Size is variable. From 6 to the 12.
5. Where is your huntsmen?? Must be taken. Slowing enemy + good damage against low-armoured goblins. Don't forget - skirmishers (archers) can shoot from the non-first ranks and have 360 degree. Against greenskins - can be used also as detachment.
Special
1. Greatswords must be taken. 15-20 with Griffon Banner. With detachment of swordsmen.
2. Pistoliers - good.
3. You have handgunners + hellblaster. Most of greenskins have light armour. May take 2 mortars - no LOS + huge template and damage against low-armoured. Or leave the cannon for shaman-hunting
Rare
1. Drop flagellants. Take one more Hellblaster. Or even Steam Tank (and roll them all). Or your can think about some DOW-ROR unit to add melee power to your troops (Ogres, pikes), or to slow the enemy (ligth cavalry, duelist). I prefer Hellblaster.