Traditionally new version of xUSSRset released on BaNaNaS or here.
In this set you'll find a lot of railroad stuff of countries that were in USSR.
Now there are:
Locomotives:
32 steam locomotives
64 diesel locomotives
26 DC electric locomotives
25 AC electric locomotives
5 dual voltage electric locomotives
*MUs:
10 DMUs
15 DC EMUs
11 AC EMUs
3 dual voltage EMUs
Wagons:
47 passenger coaches
19 mail/luggage vans
23 boxcars
12 hoppers
2 dumpcars
17 gondolas
18 platforms
37 tankers
2 bunker wagons
15 refrigerators
1 special nuclear waste wagon
(some available only when industry newgrf instaled)
Most of these have multiple models, liveries and cargo graphics.
New railway graphics (optional).

Locomotive graphics depends on situation.

New features in 0.6:
More than
8 new steam locos and some old ones have new look
6 new diesels
7 new DC and 5 new AC locos
1 new DC and 4 AC EMUs
And a lot of new wagons. including container platforms. These can haul most of types of cargoes, more available in later game years.

Graphics for 60 km/h railways.
Randomized graphics for freight wagons and cargoes.

Full support for ECS (1.2), FIRS (4.0) with individual graphics for most cargoes.

New way of coding of wagons using layers introduced in OpenTTD 1.8.0, that allows us to add new cargoes easily.
And that's not all. You can find more in game!