Hi Woodsman,
A Volkswagen Beetle was known for being very popular (many of them) and trustworthy. This speaks of these vehicles (ministries) being quite common. Therefore, it speaks of something that appears to be common as indicated by being displayed on the “left” wall. However, another dimension (whatever is on the right wall) has an influence on these vehicles (on the ministries of all these people), and that (sometimes obscure or not known to us) makes a big difference. It indicates that nothing is common about all these ministries (no look-alike) because of whatever is on the right wall.
My opinion is that God and the Holy Spirit is the “factor” that changes everything.
So yes, I think you have it spot-on if this dream is about you and your ministry and not the ministries of Christians in general.