Marriage registration in Bangladesh runs primarily through personal law — Muslim, Hindu, and Christian marriages each have their own registration framework — so "what documents do I need" doesn't have one universal answer.
That said, most cases require some combination of: national ID or birth certificate for both parties, passport-size photographs, and witnesses present at registration. For Muslim marriages, the Nikahnama itself is the central registered document, completed and signed by both parties, witnesses, and the registrar.
A detail that surprises people: registration and the religious/social ceremony are not automatically the same event — a marriage can be solemnized without being properly registered, which becomes a real problem later if either party needs to prove the marriage legally (inheritance, visas, custody).
If you're not sure which personal law framework applies to your specific situation, or whether a marriage was properly registered, that's worth confirming directly rather than assuming.