What other items might Baptists regularly engage that may be tradition or may have a Scriptural base?
A whole list of things traditional, most of which many would disagree with...
but that many have also grown so accustomed to, that they would think it
not Biblical to do them:
1) Dressing up to go assemble with one's brothers and sisters.
2) A system of hierarchy ( Doctrine of the Nicolaitanes ) in which there is a "lead pastor", "associate pastor" and so forth ( I'm not talking about the Biblical offices of humble servitude seen in the Bible ), and that authority resides in those offices that can be used to oppress or otherwise coerce their brothers and sisters. As I see it, the Roman Catholic practices / offices of "Bishop", "Archbisop, "Priest" "Cardinal" and so forth ( all the way to "Pope" ) originated with this system of thought.
3) "Tithing", in which elements of Old Testament Law are brought in to collect money for whatever are deemed to be the things of God, instead of relying on the Spirit to guide and provide such things through His people and through prayer.
4) A church building with all the comforts of home, which is supported by money that would be better-spent meeting the earthly needs of God's saints.
5) "Bible Colleges" and "seminaries" where theology is taught, and brothers and sisters actually pay someone to exercise what are, in effect, their spiritual gifts to teach them the Scriptures and "how to understand them" a certain way.
We as believers have the Holy Spirit for that ( 1 Corinthians 2:6-16, 1 John 2:20-27 ), and God's teachers and preachers should be teaching and preaching His words, and for no pay.
"Missionaries" ( what the Bible calls "evangelists" in Ephesians 4 ) are the only ones that I see as partaking of living off the preaching of the Gospel.
6) A carefully choreographed "service" that begins with songs, has a music "special", and ends with usually topical preaching that really doesn't allow for the Spirit of God to work, spontaneously, as He should.
7) Many more smaller items.