how to make a good looking bridge

Do you have any prototype pictures of what you are trying to accomplish? I highly recommend the book "Model railroad Bridges & Trestles" published by Kalmbach books. It's a compilation of articles from MRRer magazine and covers all of the basic bridges. with the basics you can build pretty much what you want even without a prototype.
 
it will be a brick wall bridge

i dont have any spc's but it will be on flat ground and it will look somthing like this New Bitmap Image.PNG
 
how wide is your space? most small gaps were filled with girder bridges,and longer ones used truss,arch or a combo of truss and girder.also era,there aren't going to be alot of brick bridges in modern era or likewise concrete bridges in the early 1900's now would there.it would be neat to see a brick bridge thats pretty big--josh​
 
In the sketch you show, my opinion is it would look better if you had two bridges, one over each track, and the space between filled with a small hill. If you had just one bridge, I think the fact that the lower track makes a horeshoe curve and doubles back under the same bridge would seem kinda weird.

Kevin
 
I believe the best way to approach this (and I am doing the same thing -- building a bridge and a trestle) is to look for prototypes, either in the field or in photographs. Study the prototype closely, and comprehend what is inherent to the bridge, and what is not. I see lots of bridges that do not look convincing because the builder did not understand the function of the various parts.