It certainly can be. In the same way life can be beautiful, so can death.
The two coexist with each other as equals and balance each other out. Neither would be able to function without the other.
All life from this planet is birthed from death. All that is dead is a result of having life lived.
Suicide in-itself isn't inherently ugly or beautiful.
Yet, for an example, in the context of suicide as an attempt to have agency over your own life, to decide and take charge of your own fate. Defy a wrong and miserable situation that oppresses you. To pursue what is true to your senses and self, all that you are and ought to believe to be.
I find that beautiful. Beauty is honest, it is also true. Things that are beautiful are things that we can admire or can be inspired from.
Another note: things that are sad can also be beautiful. This fact is obvious. So really in itself, suicide could hold any kind of sentiment depending on the context. I'm sure there are some ugly suicides, gory and grotesque. Perhaps, a pathetic pointless end of a whimper to a devoid, miserable and meaningless life. Another, as overtly romantic(yet tragic) as Romeo and Juliet, "two-star-crossed lovers" declaring that through death, their love will forever be true. That the world without each other is a world worth not living in at all.