How does one go about rendering a block/tile entity as a model in your inventory?

Use an IItemRenderer

Is there a better way to run the IItemRenderer without making a new Item(insertBlockNameHere)?

Not as of right now. IItemRenderer isn't even that hard, it's the best thing you can find as of now. (i think ;P)

Here's how I do mine:

 

TileEntitySpecialRenderer render = new PedestalRenderer();
ClientRegistry.bindTileEntitySpecialRenderer(TileEntityDisplayPedestal.class, render);
MinecraftForgeClient.registerItemRenderer(BlockPedestal.instance.blockID, new ItemRenderPedestal(render, new TileEntityDisplayPedestal()));

public class ItemRenderPedestal implements IItemRenderer {
TileEntitySpecialRenderer render;
private TileEntity dummytile;

public ItemRenderPedestal(TileEntitySpecialRenderer render, TileEntity dummy) {
	this.render = render;
	this.dummytile = dummy;
}

@Override
public boolean handleRenderType(ItemStack item, ItemRenderType type) {
	return true;
}

@Override
public boolean shouldUseRenderHelper(ItemRenderType type, ItemStack item, ItemRendererHelper helper) {
	return true;
}

@Override
public void renderItem(ItemRenderType type, ItemStack item, Object... data) {
	if (type == IItemRenderer.ItemRenderType.ENTITY)
		GL11.glTranslatef(-0.5F, 0.0F, -0.5F);
		this.render.renderTileEntityAt(this.dummytile, 0.0D, 0.0D, 0.0D, 0.0F);
	}
}
}