The Westminster Confession of Faith, which is the confessional document of Presbyterian churches (including ARP churches), states the following:
1. The light of nature showeth that there is a God, who hath lordship and sovereignty over all, is good, and doth good unto all, and is therefore to be feared, loved, praised, called upon, trusted in, and served, with all the heart, and with all the soul, and with all the might. But the acceptable way of worshiping the true God is instituted by himself, and so limited by his own revealed will, that he may not be worshiped according to the imaginations and devices of men, or the suggestions of Satan, under any visible representation, or any other way not prescribed in the Holy Scripture.
2. Religious worship is to be given to God, the Father, Son, and Holy Ghost; and to him alone; not to angels, saints, or any other creature: and, since the fall, not without a Mediator; nor in the mediation of any other but of Christ alone.
21.1-2, emphasis added
Our worship will not be perfect in this life. There are times when we may become distracted in worship, or our devotion may not be what it should. There will also be disagreements about how some of the elements of worship are employed. Nevertheless, it should be without controversy to say that in reformed churches of the Presbyterian tradition, worship should be as biblical as possible. It is neither right nor wise to go beyond the elements of worship as given to us in Scripture.
As an example of what this may look like, take a look at this past week’s worship bulletin at Midlane Park ARP Church. Since the Lord’s Supper was part of the service this past week (we celebrate the sacrament of the Lord’s Supper once a month), the order of the service was slightly different than most weeks. However, this gives an example of what a typical reformed worship service of the Presbyterian tradition might look like (if you would like to listen to the sermon that was preached, you can find it here).
It saddened me greatly, however, when a friend recently sent me a link to a worship bulletin from this past week of a church that is of the reformed and Presbyterian tradition (including subscribing to the WCF). It can best be termed a “Patriotic service,” in which the country and the American flag were honored. If certain parts of the worship service did glorify God, I fear that the other parts served to greatly obscure that. This is a service that included, among other things, the Pledge of Allegiance, a flag ceremony, and the singing of songs where the attention is primarily directed to the nation rather than God. This probably not as blatant as the church in our city that once had the following on its sign in preparation for the upcoming worship service (July 4th fell on a Sunday that year): “Celebration of America Service This Sunday.” Celebration of America? Shouldn’t we celebrating God instead during corporate worship on the Lord’s Day?
You can look at a copy of the bulletin by clicking here. I have redacted names, but you should be able to see why this is so troubling.
Gairney Bridge 
Right on target. this sort of thing used to be a lot more common. I saw a photo of a 4th of July service in a UP church in PA around 1900. The whole building was draped in patriotic bunting and flags were everywhere. No question about what was being worshiped. And this was back in the time when the UPs sang only psalms & excommunicated drinkers of alcohol.
-Dan Reuter, Nashville, Indiana