Trains are not planes and noone checks what you take with you. All things that you are able to carry for yourself and IF its not too big, can take. Bikes usually must be also REServed. DO note that f.f. couchette=bunk in nighttrain are quite cramped and you will struggle with taking too many things inside. Also: its atrain, anyone can board unchecked, so there is always chance on pickpockets and thieves-and as its not plane, they can also easily escape.

The information of @mcadv is as usual NOT true. 
All railway companies have limitations about luggage. They differ from country to country, so you should check about it in advance.
In general these rules are not enforced, but if you have a very strict conductor you might have problems if you have SUPER much luggage… 

So if you have only 2-3 trolleys with you, then it will be no problem. But if you have supersize stuff etc., then there might be problems.

And restrictions are definitely NOT like enforced like at airports.