carregar mais um. - Todas as línguas

OR "para cargar otra" (feminine). You can use "para cargar más" so you can avoid this problem.

Context?

if this is a part of the "text on the image"-context, "för att visa en annan." would be a better translation.

"un'altra" is Feminine. "un altro" is masculine. For an image, for example, is "un'altra". For "a favorite" is "un altro". You can use "per caricarne ancora" so you can avoid this problem.

NOTE: "'άλλο ένα" might not be the best translation, depending on the context (a matter of gender).