it's nice to see that you have been able to replicate flappy bird, now if you wish, you could make changes that differentiate from the original, like for example, enemies appear, or there stuff to collect.
On this jam for example, I saw a guy that made flappy bird clone, that had stuff like health bar, power ups, day night cycle, and character selection, and some years ago I found a game named beat rabbit a flappy bird like game, that the character only moves forward according to the beat of the music
and well, for developed games that are gonna be released to the public, it's best to avoid using art that you don't know the license of it. a guy on this jam got disqualified for using Pokémon sprites even though it's was slightly different than the main series
sites like opengameart.org has art assets you can get and it shows the conditions to use them
anyway I hope you didn't got discouraged from developing games and that you may be able to develop more games in the future
