My opinion is that the scene looks very good so far … things I’d take a closer look at to improve it are:
The flames and smoke seem to move in the wrong direction … the background clouds are moving to the right, which indicates that’s the direction the wind is blowing, yet the flames and smoke move to the left … however, one could also argue that the direction of the source of the explosion is counteracting the wind direction and/or that the wind is moving in the opposite direction in the distance where the clouds are.
The particles flying away from the explosion are very obviously digitally composited and look a little un-natural … it seems that a large explosion off in the distance wouldn’t really bring so many particles so close to the camera lens in clearly visible form so quickly. Also, the particles all look like sparkling embers rather than debris … perhaps there should be a combination of both … though still with consideration for the first point.
The camera shake looks un-natural … it seems the affects on the camera would be more immediate rather than lasting throughout the shot, although that’s hard to judge without sound (how many explosions the viewer will hear). It also seems the camera movement would be more of a kick-back followed by some side-to-side and up-and-down wobble that’s less extreme and that also quickly tapers off from the moment of the explosion.
I think it’s always very hard for anyone to realistically recreate something they’ve never personally witnessed … I’m not suggesting you go blow up your least favorite neighbor’s house and film it (although that would be more fun), but you probably know someone who has had some real-world war experience and personally witnessed a few large explosions … perhaps show them your scene and ask what seems real and what doesn’t.
If I recall correctly, one of the guys that frequents this forum works for the military (Michael Szalapski) … if so, even if he hasn’t personally witnessed real explosions as large as what you’re re-creating, he may have seen or have experience with creating digital simulations of large explosions.
I hope you find my feedback helpful.