Personally I like the look of a well cared for instrument what ever it is. Anything that is added to an acoustic instrument will effect its sound. If you are in a recording studio before and after you add stickers (yes the common term for self adhesive mini advertisements) you may hear the difference. To the human ear, as stated before, you won't hear any difference and after a while you will adapt to the sound if you do. If you have stickers that have great meaning or a personal connection put them on your guitar case and set it up where you play so all can see. Either way have fun and play for the thrill of making your own music .
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