Well, some other choices apart from Rebeca
Pablo Alborán
I was never a fan of him, but he has some good songs and could be what Spain needs right now. But please, I'd choose a more up-tempo song like "Volver a empezar", not the typical sleepy flamenco moaning he usually does. A song like this is very suitable for a good staging + Pablo is quite charismatic.
https://www.youtube.com/watch?v=D-4jVl-RwJA
María Sagana
I'm so surprised by this little girl. She has so commercial and international tunes and if she's good live she could bomb in Eurovision.
https://www.youtube.com/watch?v=HJxqxg2AFao
Any singer from Tu Cara Me Suena
They've shown they are quite versatile and good live with almost every song. They are all young, have a good image and a growing career in Spain. Eurovision would be a really good opportunity for them.
Roko ->
https://www.youtube.com/watch?v=ZgiTDL1G-Qk
Melody ->
https://www.youtube.com/watch?v=Vo3gKUV8iSk
Edurne ->
https://www.youtube.com/watch?v=AfFhHmAfgTU
Xuso Jones ->
https://www.youtube.com/watch?v=gTNijrS8JIs
Guys from other talent shows (The Voice, Number One....)
Raúl Gómez -> Not a fan of him, but he has a very interesting voice and his style would suit Eurovision nowadays ->
https://www.youtube.com/watch?v=Ub_IY7WXBQM
Rafa Blas -> Different style. Spain has never sent rock + his voice is amaaaazing ->
https://www.youtube.com/watch?v=J-xMAmByf7E
Paula Rojo -> Despite not reaching the final in The Voice she's been the most succesful one. So sweet and charming ->
https://www.youtube.com/watch?v=v0TFfDw_Q6s
Anael -> Another of the new and young talents who would suite quite well in ESC, but she wouldn't be my first choice ->
https://www.youtube.com/watch?v=9AeBGwgpLf8
+ Jorge González
+ Brequette
Rosa López
One of the best voices in Spain, she deserves to go again with a better song + Spain really loves her, so this would increase the interest in Eurovision like she did back in 2002. She never had good songs, but that would be solved getting good producers.
https://www.youtube.com/watch?v=xOGT9p9Qizc
Nada que Decir
This band is quite unknown. I found them by chance and they are great: simple pop songs that made you feel in a good mood. Something different and fresh for the contest.
https://www.youtube.com/watch?v=EbtX_Ogcx7g
Efecto Pasillo
Catchy latin-pop music, but not in a cheap way like we are used to. I think their songs are quite anthemic and could do well in ESC.
https://www.youtube.com/watch?v=n9qU9kVc6jM
Auryn
I don't think this is a especially good boyband (they are miiiiles better than One Direction anyway.....), but gosh, they have very good produced songs.
https://www.youtube.com/watch?v=wjiZRV0Y4ag
La Oreja de Van Gogh
Why not dreaming?
https://www.youtube.com/watch?v=cYjw9nazAPU
Diana Navarro
One of the best and most interesting voices in Spain. Unique style. But she will never go to Eurovision anyway....
https://www.youtube.com/watch?v=h5LXKh34gwI
Pasión Vega
Similar to Diana. I prefer Diana over Pasión, but this one is more likely to accept going to Eurovision.
https://www.youtube.com/watch?v=vlKOweHP4hs
Luar na Lubre
If we think about sending a song in another co-official language Galician is the choice, since Basque and Catalan music scene are not strong compared to this or are more integrated in the national scene. The celtic music they do is just delicious. Would love to see something like this.
https://www.youtube.com/watch?v=BI-Q8yBoV2o
Malú
One of the best melodic singers we have in Spain. Outstanding.
https://www.youtube.com/watch?v=tfJFbCyQRYM
Amaral
One of the best Spanish pop bands ever, with a more complex sound in their last albums. Quite unlikely they'd accept to go to ESC, but who knows, they are quite controversial right now. After Conchita it seems ESC is the perfect place for controversy!
https://www.youtube.com/watch?v=gqsYFLBJFZ8
Well, I hope I didn't miss anyone, but anyway, I think this is enough