Were there any rewards for going on a crusade aside from being forgiven for one's biblical sins?

There were indeed other incentives offered by both Church and State to individuals joining the crusades. What was offered was more often in the form of assurances of protection for the status and household/families of the individuals.

Suspension of debt payments, termination of interest payments, protection from lawsuits, and three year payment plans for debts after a two year hiatus are among the offerings.

The 1901 book Urban and the Crusaders, edited by Dana Carleton Munro, has a section on Privileges of the Crusaders. In this section he has gathered several relevant documents translated from various popes and kings concerning the types of concessions and protections offered to those individuals who 'take the cross'.

A web friendly version of this information can be found at the site Medieval Sourcebook: Evolution of Crusader Privileges, 1095-1270 at Fordham.edu.

Some excerpts (bold points mine):

First, the religious aspect, Council of Clermont 1095:

If any one through devotion alone, and not for the sake of honor or gain, goes to Jerusalem to free the church of God, the journey itself shall take the place of all penance.

Pope Eugenius III, 1146 (second crusade) expanded the incentives package :

We have also commanded that their wives and children, their property and possessions, shall be under the protection of the holy church, of ourselves, of the archbishops, bishops and other prelates of the church of God. Moreover, we ordain by our apostolic authority that until their return or death is fully proven, no law suit shall be instituted hereafter in regard to any property of which they were in peaceful possession when they took the cross.* ... Those who with pure hearts enter upon such a sacred journey and who are in debt shall pay no interest. And if they or others for them are bound by oath or promise to pay interest, we free them by our apostolic authority

The next section is from a decree by King Phillip Augustus of France, in 1188

That bishops, prelates, and clerks of the conventual churches, and knights who have taken the cross, shall have a respite of two years - dating from the first feast of All Saints after the departure of the king - in paying the debts which they owed to Jews or Christians before the king took the cross; that is, on the first feast of All Saints the creditors shall have a third of the debt, and on the following feast of All Saints a second third of the debt, and on the third feast of All Saints the last third of the debt. Also, for each one, from the day on which he takes the cross, interest on debts previously contracted shall cease.

I don't want to copy paste the entire page over, but this point may be poignant concerning individual incentives (same decree):

If a knight, who is the legitimate heir, son, or son-in-law of a knight not taking the cross, or of a widow, and who is under the jurisdiction of his father or mother, takes the cross, his father or mother shall have a respite from their debts, in accordance with the above ordinance.

This section would seem to indicated a son joining the crusades in the name of his elders would get the same protections applied to his parents debts.

One last note, since part of the question was referring to forgiveness for crimes. A privilege offered by Louis IX of France in 1270 seems to offer some limited protection to crusaders for criminal actions by turning them over to be judged within the church instead of the secular courts:

If the king, or a count, or a baron, or any lord who has the right of jurisdiction in his land, arrests a clerk, or crusader, or any man of religion, even if he is a layman, the lord ought to deliver him to the holy church, whatever may be his crime. And if the clerk has committed a crime for which the penalty is death by hanging, and is not tonsured, the secular justice ought to try him. But if be is tonsured and wears the habit of a clerk, even if he is a thief, no confession, no answer that he may make, can injure him, for he is not before his regular judges; and any confession made by one who is not before his regular judges has no value, according to the law written in the Decretals.

Some more details in the book and web page, but this gets the main idea across concerning the form of some of the incentives and protections offered to those that joined the crusades.