New and full of questions

[Xeziares]

Dear Cartographers,

first of all, I must express my admiration for this wonderful website. The name is totally perfect, and the content of this guild is even better. Hopefully I can be a worthy member.

When I was little I loved making Treasure Maps, I remember I would burn the edges of the paper so it would look really old. It was fun to do.
Now, I really love to make my own world/overland map. But I'm quite a perfectionist and just need to do things right, but that means I need to have somewhat more knowledge about geography.
I hope I'm not to "pushy" with asking questions already, but I'm just so excited about this cartography and just like to work with it as fast as possible. So lets keep it to three questions at first:

Here's the outlines of my map, and a quick sketch of the mountains and rivers:
test.jpg

First I'd like to ask you about the size. How big do you think this should be? (like how many km/miles long from the top to the end?)
Would it be possible to put at least 4 kingdoms in this piece of land?

Second, I'm note sure about the rivers. Besides mountains, what can be a source for rivers? And if you let a river come from a mountain, does it have to be a snowy mountain?
I'm not sure if my rivers are realistic enough...

Last but not least: I want a swamp.
The kind of swamp as in, for example, "Pirates of the Caribbean 2" where Tia Dalma lives.
But where can you place a swamp? Must it be near the ocean, or not, or must it be near a river. Can it be in the middle of the land, or does it need to be surrounded by water? I tried to google it, but I couldn't get a clear answer. (Perhaps it's my english, idk)

Hope you guys can help me out. And feel free to give critiques, I need them!

oh, here's btw a picture of my map's "climate":
test colours.jpg
The yellow is like desert, the green is with grass and woods, and the top is a bit emptier.. I'm not sure how to call it, it's like dead land..

Greetings,

Xeziares. (Just call me X if that's easier, haha)