Earth VS Fire

this turned out as a really nice pic of yours

colours and background
the colours represent their elements as earth and fire very well and the texture in the background is a nice add, thought you might like to mix textures to get a more unique look, because now the texture as it seems to be a stone wall texture is very clear and looks kinda like a separate part of the image....

because of the background, in the description you said that the characters are partly transparent and so you can't add a better background or they would look funny. If it happenes that you have a transparence you could select on the character layer everything that is not part of a character and then delete these parts on a basic colour under the character layer.. for example the background you have here would be a nice undercolor for the characters... and if you merge these layers the characters wouldn't be transparent any more.. (I hope you know what I mean)

poses:
I really like their poses as they are very dynamic and have slight perspective. But I suggest to practise poses in perspective. It is pretty hard to draw a complex body in movement (like a dragon flying), so it still lookes correct.
For example the lower body of the fire dragon looks really good but the head is bowed sidewards like it could not work. It looks pretty weird because the head looks like it would grow on the side of the neck or is broken. In a pose like this the head would be more frontal in perspective.

Also I thought it would look good if the fire dragon had it's head bowed down towards the earth dragon, that would add a feeling like they would be about to fight each other and communicate better with each other.

details:
I like how you added the big scales on both of them. They are simple but therefore good to see and not too complex to destroy the focus on their main design. (I have seen a lot of pictures where people get crazy with scales lately ;D )

Something that looks also really good are the glowing fire tips of the firedragons spines (or how to call it), they add a mysterious touch to the design and support the firelike look.
As for the earth dragon I agree with you that it would be cool to add some kind of skin/scale armor to it to let it look more earthy/rock-like and stronger in comparison to the beautiful and slight built fire dragon, it would be a great contrast between them both.

Something I would change on the earth dragon is the tail. I really like the tail but the green colour kinda does not fit the overall brown dragon. The fire dragon is also overall red with orange inbetweens.
If you want to keep the green crystal like tail then I think it would be better to also add some more green crystal parts on it's body... maybe on some parts the skin is broken and under it there you can see some crystal parts or so.
Like with the fire dragon, it also has some unique parts like the glowing spines but there is more than one which looks most times better than have just one like the crystal tail....

overall:
a sweet image with a warm feeling and two beautiful dragons.

hope this critique is helpfull and not too long <img src="e.deviantart.com/emoticons/a/a…" width="19" height="19" alt="" title="Sweating a little..." /> sorry kinda got carried away since this is my first critique and I don't know how to explain things shortly in english so it is clear.
You are really improving and I wish you good luck to get better <img src="e.deviantart.com/emoticons/s/s…" width="15" height="15" alt="" title=" (Smile)" />