I have a few suggestions too.
AUSTRIA: Zoe
She participated this year but lost to The Makemakes & Dawa. Like her last entry she could include french folky beats in her tune.
POLAND: Aneta Sablik
Although she won German Idol back in 2014, but she has a power range ala Beyoncé and she's actually polish and would get many many points from german countries.
GERMANY: Pino Severino
An X-Factor and German Idol reject but with a good voice. Maybe he could finally have some luck at the ESC. Points from Italy maybe?
SWITZERLAND: DJ Antoine
Maybe with special guest popstar. He's well known in Europe, so why not?
BELGIUM: Kate Ryan
She participated years ago but is actually well known for her dance hits and she's sexy.
NETHERLANDS: Within Temptation/Sharon den Adel
Either with her band or solo. It could work for the Goth-Queen! And they have fans all over Europe.
FINLAND: Kivimetsän Druidi/ Leeni-Maria Hovila
And another metal band with a female lead singer. Take an ethnic song and she could surprise you solo aswell.
PORTUGAL: Nelly Furtado
Yes, the worldwide known singer. Actually from Canada but with portuguese roots - remember Celine Dion (Canada/Switzerland). Her career has been on a low - an ESC win could do wonders.
UK: Rizzle Kicks
UK, actually with a modern hip-hop act. They're not any worse than past UK entries.
SWEDEN: Mando Diao
Although one of the front-leaders left the band they are still relatively successful. An 80's influenced rock song like 'Black Saturday' could be the entry for their hosting country.
FRANCE: Zaz
The french singer, most known for her hit 'Je Veux' could perform an acoustic folk song in french and chart higher than her predecessors.
DENMARK: Medina
I'm with KillingYourCareer on this one. Screams 'Europhia' nostalgia.
AUSTRALIA: Lenka
If Australia has the chance to participate again, they should send Lenka (known for hit 'The Show'). Though still relatively unknown she could have a try at the ESC.
IRELAND: The Corrs
Irish band relatively known for past hits like 'Breathless' or 'Summer Sunshine' they could have some sort of comeback.
NORWAY: Maria Mena
She could convince the audience with a balladesque song like Boggie (Hungary) had this year. Maybe add a duet partner and it could be a hit.
TURKEY: Tarkan
Who doesn't know his 90s hit 'Şımarık (Kiss Kiss)'? Another comeback option for the ESC and still good looking.
SPAIN: Enrique Iglesias
Actually really from Spain and like Furtado blessed with worldwide hits he could try the ESC with an R&B pop number to make himself a bit relevant again.