Everything that is good, moral, encouraging... is from God.
Philippians 4:8 Finally, brethren, whatever things are true, whatever things
are noble, whatever things
are just, whatever things
are pure, whatever things
are lovely, whatever things
are of good report, if
there is any virtue and if
there is anything praiseworthy—meditate on these things.
I also wanted to add, that each Christian song of praise should be genuine. Sometimes it seem as though Christian music can make the glory of Christ trite. Anything that glorifies or praises God should come genuinely from your soul; if you do not have the words or the feelings to express it, then are you risking taking God's name in vain by forcing a song?
Let your artistic skill move you to what you want to express; do not force an expression out of a feeling of obligation that everything has to mention God. God is in everything anyway; He created all things. Narrowing your focus on, say, only writing hymn-like music can take away from meditating on the smallest of some of God's creations. And then you might lose sight of God and how powerful he truly is.
Country songs will go through a long list of all they lost; you could make counter-country music, counting your blessings on all the good things that have happened. God tells us to offer the Sacrifice of Thanksgiving. Writing a song about gratitude, even without God's name mentioned, can still be wholesome and good.
Ecclesiastes 5:2 Do not be rash with your mouth, And let not your heart utter anything hastily before God. For God
is in heaven, and you on earth; Therefore let your words be few.