Scearch the DLS for "Diesel Locomotive Depot" by piegon. Its an awesome 5 track repair shed. Based on an Australian design, but it works well for North American routes as well.
Also look for the "Car Shop", a track spline which gives you a 3 track shed any length you want.
Searching for engine or loco, and shop or shed are great keywords to search by.
Check out the engine facility screenshots thread, you might see something you like!